Step 1

Heat oven to 350°. Grease a 9×13 inch baking pan.
Whisk together flour, baking powder, baking soda, salt, and sugar.

Step 2

Stir in melted butter, sour cream, eggs, and vanilla until smooth. Pour into prepared pan.
Sprinkle apples on top of batter.

Step 3

In a medium bowl, stir together all topping ingredients until thoroughly mixed. Sprinkle on top of apples.

Step 4

Place pan in oven and bake for 40 to 45 minutes or until a toothpick inserted in the center comes out clean.

Step 5

Make glaze. Combine all ingredients in a small saucepan and place over medium heat until sugar and butter are melted. Drizzle over coffee cake. Serve warm or at room temperature.