Grease a medium-sized baking dish with softened butter. Set aside.
If using frozen cherries, place thawed and drained cherries in a large bowl and add one tablespoon sugar. Add 1-2 tablespoons of almond-flavored liqueur, if using, or gently press the juicy cherries to release the remaining liquid and toss to combine. Set aside.
Place the top oven rack in the center position and pre-heat oven to 350°F.
Add eggs, milk, vanilla extract, almond extract, and flour in a high-powered blender or food processor. Pulse just until all ingredients are thoroughly combined and foamy. Do not over-blend.
Arrange the cherries in the bottom of the greased baking dish and pour the smooth batter on top.
Add the slivered almonds in a single layer on top and gently press down with a spatula so they are mostly submerged in the batter, but still near the top, as shown.
Place the baking dish in the preheated oven and bake for 40-45 minutes.
Once the top looks golden brown, remove it from the oven and cool for 15 minutes before slicing. Dust with powdered sugar right before serving. Enjoy!