Preheat an oven to 350°F Grease and flour a 9-inch round springform pan or square baking pan or baking dish (see Note).
To make the streusel, in a bowl, stir together the flour, brown and granulated sugars and cinnamon. Add the butter and, using a pastry blender or your fingers, cut or rub in the butter until coarse crumbs form. Set aside.
To make the cake, in a bowl, stir together the flour, granulated sugar, baking powder and salt. In another bowl, using an electric mixer on medium speed or a wire whisk, beat the egg, melted butter, milk, vanilla and almond extract until creamy, about 1 minute. Add to the flour mixture and beat just until evenly moistened. There should be no lumps or dry spots. Do not overmix.
Spoon the batter into the prepared pan and spread evenly. If using a springform pan, arrange the peach slices in concentric circles from the pan sides to the center. If using a square pan, arrange the slices in rows. Gently press the slices into the batter. Sprinkle evenly with the streusel.
Bake until the topping is golden brown and a toothpick inserted into the center of the cake comes out clean, 40 to 45 minutes. Transfer the pan to a wire rack and let cool for 20 minutes. Remove the sides of the springform pan, if using. Serve the cake warm or at room temperature, cut into wedges or squares. Makes one 9-inch cake.
Note: If using a glass baking dish, reduce the oven temperature to 325°F.