Grape Galette with Almond Cream

Name: Grape Galette with Almond Cream
Ingredients: 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)