Preheat the oven to 350ºF. Lightly grease an 8-inch round cake pan. Set aside.
Melt 4 tablespoons (57g) butter in a small pot over medium heat. Once melted, add ½ cup (100g) light brown sugar. Stir to combine. Cook over medium heat for 3 minutes, stirring occasionally, until the sugar blends into the butter and the mixture darkens slightly in color.
Reduce the heat to low and add 2 tablespoons (30g) amaretto. Whisk until smooth and simmer for 1 minute. Turn off the heat.
Pour the mixture into the prepared cake pan and smooth it into an even layer. Transfer to the freezer for 15 minutes.
Assemble cherries:
Combine halved cherries, 1 tablespoon (15g) granulated sugar, 1 tablespoon (7g) cornstarch, and ½ teaspoon almond extract in a bowl. Stir to coat and set aside.
Make the batter:
Sift 1 cup (120g) all-purpose flour, 1½ teaspoons baking powder, and ¼ teaspoon kosher salt into a small bowl. Set aside.
Add 4 tablespoons (57g) room-temperature butter and ½ cup (100g) granulated sugar to a large bowl. Use an electric hand mixer to cream them together. Add 1 egg and beat until smooth.
Add half the sifted dry ingredients and beat with the mixer until just combined. Add ½ cup (120g) whole milk and beat until just combined. Add the remaining dry ingredients along with 1 teaspoon vanilla extract and ¾ teaspoon almond extract. Beat until just combined. Don’t overmix! Fold in the chocolate chips and almonds.
Assemble the cake:
Remove the cake pan from the freezer. Arrange the cherries on top and press them into the caramel layer to form a tightly packed layer.
Pour the batter on top and smooth into an even layer. Scatter ½ cup (45g) sliced almonds on top.
Bake the upside-down cake:
Transfer the cake to the oven and bake for 45 to 50 minutes until a toothpick inserted into the center comes out clean.
Let the cake stand at room temperature for 60 minutes. The cake should still be warm to the touch. Note: Cherry cake can be very syrupy, so be sure to let it cool.
Flip the cake:
Place a large plate over the cake pan and carefully invert the cake onto the plate.
To serve:
Slice the cake and serve it with whipped cream or vanilla ice cream, if desired, though it’s delicious with no accompaniments.