Preheat your oven to 375°F (190°C). Generously butter a 9-inch pie plate or a 9-inch round baking dish. Sprinkle the bottom of the dish with 1/4 cup of granulated sugar.

Arrange the pitted cherries in a single layer over the sugared bottom of the prepared dish. If using unpitted cherries, ensure they are evenly distributed.

In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.

In a separate large bowl, whisk the eggs and the remaining 1/4 cup of sugar until pale and slightly frothy. Whisk in the milk, vanilla extract, and optional liqueur until just combined. Do not overmix to avoid creating too many air bubbles.

Gently whisk the dry ingredients into the wet ingredients until the batter is smooth and just combined. The batter should be quite thin.

Pour the batter evenly over the cherries in the baking dish. It may seem like there isn't enough, but the batter will rise significantly.

Bake for 40 to 45 minutes, or until the clafoutis is puffed up, golden brown around the edges, and the center is mostly set (it should have a slight wobble). Do not open the oven door during the first 30 minutes.

Remove from the oven and let cool slightly on a wire rack for at least 15 minutes before dusting generously with additional powdered sugar and serving warm.