For the crepes, add the flour, sugar, salt, milk, eggs, butter and vanilla extract in a large mixing bowl. Whisk batter well to remove any lumps, and then let the batter rest for at least 1 hour to ensure tender crêpes. In a small, flat, round crêpe pan, heat the pan over medium heat and grease lightly with butter or oil to prevent sticking or, in the case of nonstick pans, to add flavor. With a ladle or small measuring cup, quickly pour a small amount of batter into the pan. Immediately tilt and swirl the pan to spread the batter in a thin, even layer that just covers the bottom of the pan. Cook for a few minutes, and then check the doneness of a crepe by carefully lifting one edge and looking underneath it for a golden color with specks of light brown. With a spatula, loosen the edge of the crêpe from the pan, turn, and cook on the other side until golden. Crêpes are easily made in advance. Cool crêpes completely on baking sheets. Stack crêpes with parchment or waxed paper between each one. They can be refrigerated or frozen for later use.
To make the apple filling, melt the butter in sauté pan over low heat. Add the apples, sugar, and cinnamon, and sauté over medium heat until apples are golden brown on both sides. Fill each crêpe with 2 tablespoons of apple filling and top with 3 tablespoons of toasted almond mascarpone. Garnish crêpes with lemon zest and serve.
For the toasted almond mascarpone, whip the mascarpone and fold in the almonds.
Note: The crêpes and apple filling can be made ahead of time. Let the crêpes and filling return to room temperature if they have been refrigerated or frozen.