Pro tips and easy variations
Using very ripe bananas—speckled or even mostly brown—is the key to deep banana flavor and a moist crumb. Under‑ripe bananas won’t mash as smoothly and will give a milder flavor.
Keep the crumb topping mixture in the fridge until you’re ready to sprinkle it over the batter; cold butter creates better, chunkier crumbs that hold their shape instead of melting flat.
Easy variations:
- Add 1/2–1 cup chopped nuts (walnuts or pecans) to either the batter or the crumb topping for extra crunch.
- Stir in a handful of mini chocolate chips to the batter for a banana‑chocolate twist.
- Add a pinch of nutmeg or cardamom to the crumb topping for a more complex warm‑spice flavor.
- Drizzle the cooled cake with a simple vanilla glaze (powdered sugar + milk + vanilla) for a coffee‑shop finish.
Storage and make‑ahead
This cake keeps well and is great for making ahead for breakfasts, brunches, or snacks.
- Room temperature: Store cooled cake tightly covered at room temperature for 2–3 days. The sour cream and bananas keep it moist, while the crumb topping stays pleasantly crisp.
- Refrigerator: For slightly longer storage, refrigerate in an airtight container for up to 4–5 days; bring to room temperature before serving for best texture.
- Freezer: Wrap individual slices or the whole (cooled) cake tightly in plastic wrap and then foil, and freeze for up to about 2 months. Thaw overnight in the fridge or at room temperature, and refresh briefly in a low oven if you want to re‑crisp the topping.
FAQ
Can I bake this in a 9×13 pan instead of 9‑inch?
Yes, but the cake will be thinner and may bake faster. Start checking around 30–35 minutes and pull it once a toothpick comes out clean.
Can I substitute yogurt for sour cream?
Full‑fat Greek yogurt can typically replace sour cream 1:1 and will still give moisture and tang. The crumb may be slightly different, but the cake will remain tender.
How do I know when the cake is done?
The crumb topping should be golden, and a toothpick inserted in the center should come out clean or with a few moist crumbs. If it comes out with wet batter, continue baking and check again in a few minutes.
Can I add a filling layer instead of just topping?
You can sprinkle half the crumb mixture over half the batter, then top with the remaining batter and the rest of the crumbs for a layered coffee‑cake effect. Adjust bake time slightly if the cake is thicker.