Preheat the oven to 350F and line a muffin or cupcake pan with liners.
Wash and dice apples. Peel optional.
In the bowl combine dry ingredients: flour, baking powder and cinnamon powder. Set aside.
In the separate bowl whisk eggs with sugar until mixture is fluffy. Add vegetable oil and sour cream and mix until combine.
Add dry ingredients and mix again. Be careful not to overmix the better. Fold in the apples in the dough.
Divide the better evenly into lined muffin or cupcake pan, filling 2/3 full.
Sprinkle streusel over muffins immediately before baking.
Bake 25-30 min at 350F, or until a toothpick inserted in the center comes out clean.
Let muffins cool in the pan for 5 minutes, then transfer to wire rack and cool to room temperature.