1 3/4 cups all-purpose flour, plus more for dusting
5 tablespoons sugar
1 teaspoon salt
10 tablespoons cold unsalted butter, cut into small pieces
1 large egg yolk, for brushing
1/2 cup plus 2 tablespoons sliced almonds
1/4 cup plus 2 tablespoons sugar
1 large egg yolk
2 tablespoons unsalted butter, at room temperature
1 1/2 teaspoons pure vanilla extract
1 teaspoon finely grated lemon zest
1 pound seedless grapes (red, purple and/or green; about 2 cups)