This 5-ingredient Earth Day Evening Bake is my kind of weeknight comfort food: hearty, budget-friendly, and almost entirely hands-off. It leans on humble pantry staples—potatoes, onions, canned lentils, and a bit of cheese—to create a bubbling, umami-rich golden layer that hides a tender, fibrous interior. Think of it as a Midwestern nod to French gratins and British cottage pies, but plant-forward and streamlined for real life. Everything bakes together in a deep glass casserole dish, developing that glossy, caramelized crust that makes the whole kitchen smell like you’ve been cooking for hours, even though the oven did most of the work.
Serve this Earth Day Evening Bake straight from the oven with a simple green salad dressed in a bright vinaigrette to cut through the richness. A side of steamed or roasted seasonal vegetables—like broccoli, green beans, or carrots—adds color and texture. If you’d like more substance, offer warm crusty bread to swipe through the savory juices at the bottom of the dish. For drinks, a light red wine, a malty beer, or sparkling water with lemon all pair nicely with the earthy flavors and the cheesy, golden top.
5-Ingredient Earth Day Evening BakeServings: 4
Ingredients
2 tablespoons olive oil, plus extra for greasing
1 large yellow onion, thinly sliced
3 large russet or Yukon Gold potatoes (about 2 pounds), thinly sliced
2 cans (15 ounces each) cooked brown or green lentils, drained and rinsed
2 cups shredded sharp cheddar cheese (or another melty cheese of your choice)
Directions
Preheat your oven to 400°F (200°C). Lightly grease a deep 2 to 3-quart glass casserole dish with a little olive oil to help prevent sticking and to encourage a glossy, caramelized crust.
In a large skillet, warm 2 tablespoons olive oil over medium heat. Add the sliced onion and a pinch of salt if you like. Cook, stirring occasionally, until the onions are soft, golden, and starting to caramelize at the edges, about 10 to 12 minutes. This step builds the umami base for the bake.
While the onions cook, scrub the potatoes well and thinly slice them into rounds, about 1/8-inch thick. You can leave the skins on for more fiber and an Earth Day nod to using the whole ingredient. Pat the slices dry with a clean towel to prevent excess moisture in the casserole.
Spread the caramelized onions evenly over the bottom of the prepared glass casserole dish, creating a savory foundation that will infuse the layers above with flavor as everything bakes.
Scatter the drained and rinsed lentils over the onions in an even layer. Gently press them down with the back of a spoon so they settle into the onions, forming the fibrous, hearty interior that will sit beneath the golden top.
Arrange the sliced potatoes in overlapping layers over the lentils, like shingles on a roof. This creates the concealed top that will turn into a bubbling, umami-rich golden layer as it bakes. Make sure the potatoes cover the lentils fully so the interior stays moist.
Sprinkle the shredded cheddar cheese evenly over the top layer of potatoes. Try to cover as much surface as possible; this cheese will melt, bubble, and brown into that glossy caramelized crust you’re after. If any potato edges are exposed, a light sprinkle of cheese over them helps protect them from drying out.
Cover the dish tightly with foil and place it on the middle rack of the preheated oven. Bake for 35 minutes, allowing the potatoes to steam and soften while the flavors mingle and the lentils soak up the onion juices.
After 35 minutes, carefully remove the foil (watch for steam). Return the uncovered casserole to the oven and bake for another 20 to 25 minutes, or until the cheese is deeply golden, bubbling vigorously around the edges, and the potatoes are completely tender when pierced with the tip of a knife.
Let the bake rest for at least 10 minutes before serving. This short rest allows the bubbling umami-rich golden layer to settle slightly and makes it easier to scoop clean portions, revealing the succulent, fibrous lentil-and-onion interior hidden beneath the glossy caramelized crust.
Variations & Tips
You can adapt this Earth Day Evening Bake easily while keeping its 5-ingredient spirit. For a smokier, more pronounced umami note, swap half of the cheddar for smoked cheddar or smoked gouda. If you prefer a slightly lighter top, use part-skim mozzarella for extra stretch, paired with a smaller amount of sharp cheddar for flavor. To change the character of the dish, use sweet potatoes instead of white potatoes; they’ll caramelize more quickly and add natural sweetness against the savory lentils. If you don’t have canned lentils, you can use about 3 cups of well-cooked homemade lentils—just be sure they’re tender and well-drained so the casserole doesn’t become watery. For a bit more texture, leave some lentils slightly firmer; they’ll hold their shape under the creamy potatoes and cheese.
To keep the ingredient list to five items, any seasoning beyond salt and pepper should come from your pantry staples, but you can still play: a light sprinkle of dried thyme or smoked paprika over the lentils before layering the potatoes adds depth without complicating the process. If you eat dairy-free, use your favorite plant-based shredded cheese that melts well; just be aware that some vegan cheeses brown less, so you may want to briefly broil the top at the end (watch very closely to prevent burning).
Food safety tips: Let the casserole cool slightly before handling the hot glass dish; place it on a trivet or thick towel, not a cold surface, to avoid thermal shock. Because this bake is dense, check that it’s heated through to the center; the internal temperature should reach at least 165°F (74°C) if you’re reheating leftovers. Store leftovers in a covered container in the refrigerator and eat within 3 to 4 days. Reheat individual portions in the oven or toaster oven at 350°F (175°C) until hot and bubbling; avoid reheating in the glass baking dish directly from the refrigerator to a very hot oven to reduce the risk of the glass cracking.
