To make the filling: Bring a small saucepan of water to a boil. Dip the fully ripened peaches in the water for 10 seconds so that the peel loosens. Remove from the water, and allow to cool completely, about 10 minutes. Remove the peel and pit, and then chop. Combine the chopped peaches with the lemon juice, 1/2 cup sugar (100g) and ¼ flour (32g). Set aside.

Prepare a 9”x 9” x 3” (23cm x 23cm x 7.62cm) baking pan by lining it with parchment paper. Preheat oven to 350°F (176°C).

To make the cake: Sift together the flour, baking powder, baking soda and salt in a large bowl. In a separate bowl, cream together the butter and sugar. Add the sour cream, vanilla and eggs, and beat until smooth, about 2 minutes. Add the dry ingredient mixture one spoonful at a time, beating with the mixer between additions until all of the dry ingredients are incorporated. Set aside.

To make the topping: Using a food processor or a pastry stirrup, combine the brown sugar, butter and flour until the mixture resembles coarse meal. Stir in the chopped pecans and cinnamon. Set aside.

To assemble the coffee cake, pour the prepared peaches to the baking pan lined with parchment. Dot the top of the peach layer evenly with dollops of the cake batter. Spread the batter lightly for a smooth layer. Sprinkle the crumbled brown sugar topping evenly over the cake layer.

Place the coffeecake in the preheated oven and bake for 50-60 minutes. Cake is ready when toothpick comes out clean out of center. 

Dust with powdered sugar once the cake is fully cool right before serving.