My mother-in-law surprised us with this last Sunday morning and my kids have been begging for it ever since. It's become our new weekend tradition.

This oven baked 6-ingredient vintage sour cream coffee cake is exactly the kind of thing my mother-in-law shows up with on a lazy Sunday morning and somehow makes it feel like a holiday. It has that old-school church-basement, Midwestern potluck vibe: tender, tangy sour cream cake with a buttery cinnamon-sugar streusel on top, baked in a simple white casserole dish. It’s the kind of recipe you can memorize, whip up before the kids are even out of pajamas, and turn into a weekend tradition without needing a special trip to the store.

Serve this coffee cake warm, straight from the casserole dish, with hot coffee for the adults and cold milk or hot cocoa for the kids. A bowl of simple fresh fruit or a quick fruit salad on the side keeps it feeling a little lighter and more brunchy. If you’re hosting, pair it with scrambled eggs or a basic egg bake so you’ve got something savory to balance the sweet. Leftovers (if you have any) are great reheated for a few seconds in the microwave and make an easy grab-and-go breakfast with a travel mug of coffee.

Servings: 8-10

1 cup granulated sugar

Preheat your oven to 350°F (175°C). Lightly grease a 9x13-inch white casserole or baking dish with butter or nonstick spray. This is the same style of dish my mother-in-law uses when she drops this off on Sunday mornings.

In a large mixing bowl, cream together the softened butter and granulated sugar with a hand mixer or sturdy spoon until light and fluffy, about 2–3 minutes. This step helps give the cake its tender, vintage bakery-style crumb.

Beat in the eggs one at a time, mixing well after each addition. Scrape down the sides of the bowl so everything is evenly combined.

Add the sour cream to the bowl and mix until smooth and creamy. The batter may look a little thick and silky—that’s exactly what you want. The sour cream is what keeps the cake moist and gives it that old-fashioned tang.

Sprinkle the flour and baking powder over the wet mixture. Gently fold and stir just until no dry streaks of flour remain. Avoid overmixing so the cake stays soft and tender. The batter will be thick but spreadable.

Spread the batter evenly into the prepared casserole dish, smoothing the top with a spatula or the back of a spoon. It doesn’t have to be perfect; the streusel will cover any uneven spots.

In a small bowl, make the simple streusel topping: stir together the brown sugar and ground cinnamon with a fork until well combined and no big clumps remain. This is the crumbly layer that bakes into that golden, slightly crunchy top you see in the photo.

Sprinkle the cinnamon-brown sugar mixture evenly over the top of the batter, covering the entire surface. If you like a little more texture, gently press some of it into the batter with your fingertips while leaving the rest loose on top for a crumbly finish.

Bake in the preheated oven for 25–30 minutes, or until the top is golden and the streusel looks set and slightly crisp around the edges. A toothpick inserted into the center should come out mostly clean, with just a few moist crumbs attached.

Remove the coffee cake from the oven and let it cool in the dish on a wire rack for at least 10–15 minutes. This helps it set up so you can scoop or slice clean pieces while it’s still warm and cozy.

Serve warm, scooped or cut into squares directly from the white casserole dish. This is exactly how my kids like it on Sunday mornings—still a little steamy, with the cinnamon sugar melting into the soft, golden cake. Cover leftovers tightly and store at room temperature for up to 2 days, or refrigerate for up to 4 days.

To keep this a true 6-ingredient recipe, the base is very simple, but you can play with it once you’ve made it a few times. For a slightly richer flavor, swap half of the granulated sugar in the batter for brown sugar. If your family loves nuts, sprinkle 1/2 cup chopped pecans or walnuts over the streusel before baking for extra crunch. You can also add 1 teaspoon vanilla extract to the batter if you don’t mind technically going over six ingredients; it adds a classic bakery aroma. For a lighter version, use light sour cream and reduce the sugar in the streusel by a couple of tablespoons, but keep in mind the texture and sweetness will change slightly. This coffee cake reheats well in the microwave in 10–15 second bursts; avoid overheating so it doesn’t dry out. For food safety, store the cooled cake tightly covered at room temperature for up to 2 days; after that, refrigerate because of the sour cream and eggs. Always let the cake cool on a heat-safe surface, and make sure it reaches the minimum bake time and passes the toothpick test so the center is fully cooked. If you’d like to prep ahead, you can mix the dry ingredients and the streusel the night before, then quickly stir together the wet ingredients in the morning and bake fresh so it’s ready just as everyone wanders into the kitchen.