PreparationFor strawberry jam: Cook strawberries and sugar in a medium saucepan over mediumhigh heat, stirring occasionally, until jamlike in consistency, 12-15 minutes. Remove from heat; stir in lime zest and juice. Pour into a shallow bowl and let cool. For biscuits: Preheat oven to 400°. Whisk sugar, baking powder, salt, and 2 1/4 cups flour in a large bowl. Add butter and lime zest and blend with your fingertips until coarse crumbs form. Add buttermilk and, using a fork, mix until just combined. Transfer to a lightly floured surface. Gently knead just until a shaggy, moist dough forms, about 4 times. Roll out dough about 1/2" thick. Using a 2 1/2" biscuit cutter or inverted glass, cut out rounds. Gather scraps and repeat rolling and cutting until all dough is used. Place biscuits on a parchment-lined baking sheet. Using your thumb, make a large divot in the center of each biscuit; brush with egg and sprinkle liberally with raw sugar. Spoon a scant 1 teaspoon strawberry jam into each divot. Bake biscuits until golden brown, 18-22 minutes. Serve warm with vanilla ice cream, if using, and remaining jam. DO AHEAD: Jam can be made 3 days ahead. Cover and chill.
PreparationFor strawberry jam: Cook strawberries and sugar in a medium saucepan over mediumhigh heat, stirring occasionally, until jamlike in consistency, 12-15 minutes. Remove from heat; stir in lime zest and juice. Pour into a shallow bowl and let cool. For biscuits: Preheat oven to 400°. Whisk sugar, baking powder, salt, and 2 1/4 cups flour in a large bowl. Add butter and lime zest and blend with your fingertips until coarse crumbs form. Add buttermilk and, using a fork, mix until just combined. Transfer to a lightly floured surface. Gently knead just until a shaggy, moist dough forms, about 4 times. Roll out dough about 1/2" thick. Using a 2 1/2" biscuit cutter or inverted glass, cut out rounds. Gather scraps and repeat rolling and cutting until all dough is used. Place biscuits on a parchment-lined baking sheet. Using your thumb, make a large divot in the center of each biscuit; brush with egg and sprinkle liberally with raw sugar. Spoon a scant 1 teaspoon strawberry jam into each divot. Bake biscuits until golden brown, 18-22 minutes. Serve warm with vanilla ice cream, if using, and remaining jam. DO AHEAD: Jam can be made 3 days ahead. Cover and chill.