Preheat oven to 180°C (350°F). Butter the baking dish generously. Add sugar and tilt to coat. Tip out excess.
Pit the cherries. Toss with sugar, kirsch or lemon juice, and vanilla. Rest 10 minutes.
Whisk eggs and sugar together for 1–2 minutes until pale and slightly thickened.
Add flour and salt. Whisk until completely smooth.
Gradually whisk in whole milk and heavy cream until batter is thin and smooth.
Add melted butter, vanilla, lemon zest, and almond extract if using. Whisk until fully combined.
Rest the batter for 10 minutes.
Arrange macerated cherries in an even single layer across the prepared dish. Pour any cherry juices over them.
Pour batter slowly and evenly over the cherries.
Bake 38–42 minutes until puffed and golden at the edges and just barely set in the center with a faint wobble.
Cool briefly. Expect deflation — this is normal.
Dust generously with powdered sugar just before serving.
Serve warm or at room temperature with crème fraîche, cream, or ice cream alongside.