Preheat oven to 350 F. Use 9x13 inch baking pan or 9 inch springform pan.
In a medium bowl, beat 6 tablespoons of very soft, room temperature butter, 1 cup brown sugar and 2 eggs on high speed for about a minute until fluffy and light in color. Add Greek yogurt and beat some more to combine.
In a separate bowl, combine 2 cups flour, baking soda, baking powder, 1 teaspoon cinnamon, and just a pinch of salt.
Add dry ingredients to wet ingredients and stir to combine. Fold in chopped apples.
To make crumb topping: In a small bowl, combine 1 teaspoon cinnamon, ⅔ cup brown sugar, ⅔ cup flour and mix to combine. Add 5 tablespoons of melted unsalted butter and mix until the mixture is very crumbly and has coarse texture. Add more flour if necessary.
Grease 9x13 inch baking pan or 9 inch springform pan. Pour cake batter into the pan and top with the crumb topping. Bake for about 50 minutes until the toothpick inserted in the center of the cake comes out clean.
Optional: Drizzle with caramel sauce.