Preheat the oven to 375 degrees F. Toss the cherries, whiskey and bitters in a bowl and let sit at room temperature, stirring occasionally, about 30 minutes. Drain the cherries and reserve the liquid. Butter a 10-inch pie plate and arrange the cherries in the plate in a single layer.
Whisk the half-and-half, reserved cherry liquid, eggs, flour, sugar, lemon zest, orange zest and salt in a large bowl. Pour over the cherries and bake until the edges start pulling away from the sides of the pan and the top is lightly golden, about 45 minutes. Remove from the oven and sprinkle with the coarse sugar. Switch the oven to the broiler setting and broil the clafoutis until golden brown and bubbling, 1 to 3 minutes. Let cool at least 10 minutes.