Preheat the oven to 375 degrees F.
Grease an 8-inch square baking dish or 9-inch cake pan (I used a 9-inch springform) with butter.
In the bowl of an electric mixer, mix the sugar and lemon zest for a few seconds to infuse flavor. Add the butter and beat until light and creamy, about 3 minutes.
Add the egg and beat until combined. Stir in vanilla and almond extract.
Add half of the flour***, all of the baking powder, and salt, followed by half the milk and mix until just combined. Repeat with the remaining flour and milk and mix until combined.
Fold in the peaches and blueberries into the batter, trying not to overmix.
Transfer the batter to the prepared baking dish and smooth the top with a spatula.
In a small bowl, make the topping by whisking together the sugar and cinnamon. Evenly sprinkle the sugar mixture over the batter and bake for 40 to 45 minutes, until the center is set and springs back or a toothpick inserted into the middle of the cake comes out clean.
Allow to cool slightly and serve warm or at room temperature with a scoop of ice cream or whipped cream, if desired.