Apple-Cinnamon Coffeecake

This coffee cake is best served warm. Before cooking, cool completely, wrap (still in the mold) in foil and leave at room temperature for one day or freeze for up to three months. To preheat the defrosted cake, unwrap and bake at 250 ° C for 15-20 minutes.
Preheat the oven to 350 degrees.To make the pie, lightly pour 1 1/2 cups flour into dry measuring cups; smooth with a knife. Combine the flour and the next 4 ingredients (with the added salt) in a large bowl, stirring with a whisk. Make a well in the center of the mixture. Combine the milk, melted butter, vanilla and egg, stirring with a whisk; add to the flour mixture, stirring until it becomes moist. Wrap the apple in it. Pour the batter into an 8-inch square baking dish greased with cooking spray.To make the streusel, combine the brown sugar, 2 tablespoons of flour, and 1/2 teaspoon of cinnamon; beat the butter using a pastry blender or 2 knives until the mixture resembles coarse flour. Sprinkle the dough evenly with streusel. Bake at 350 ° C for 45 minutes or until a wooden stick inserted in the middle comes out clean. Let cool in the pan on a wire rack for 10 minutes before serving. Serve warm.