Step 1

Preheat the oven to 350 degrees Fahrenheit. Grease an 8-inch square baking dish with cooking spray. Dust the bottom and sides with 1 tablespoon of flour and shake off the excess.

Step 2

In a large bowl, beat the softened butter and brown sugar for the cake with an electric mixer at medium speed until light and fluffy. About 5-8 minutes.

Step 3

Beat in the egg, followed by the sour cream, vanilla yogurt, and vanilla extract. Beat until well combined.

Step 4

Sift the cup of flour, 3/4 teaspoon cinnamon, baking soda, and salt into a separate bowl. Gradually add the dry ingredients to the butter mixture and gently mix to combine. Mix in the apples. Pour the batter into the prepared dish.

Step 5

For the topping, mix all the topping ingredients with a fork until they turn into a crumbly mixture. Sprinkle it evenly over the batter.

Step 6

Bake for 35 to 40 minutes, or until a toothpick inserted into the center comes out clean. Let the cake cool in the pan for 10 minutes. Remove the cake from the dish and place it on a wire rack to cool completely. Slice, serve, and enjoy!