This free-form tart is intended to show that homemade pastry is 100 percent doable, even for the novice baker. Keeping the peels on the apples, using whole-wheat flour, and adding walnuts to the recipe adds a wholesome touch to the finished tart. Feel free to leave out the walnuts if you prefer, just stir the additional sugar and cinnamon into the apples. Serve the tart with gently whipped cream or ice cream for dessert or enjoy it for breakfast with plain Greek yogurt .
Set the baking sheet with chilled dough on your work surface. Spread the walnut mixture in a circle over the pastry about 2 inches from the border. Arrange the apple slices over the walnuts, pouring any liquid in the bowl evenly over the top. Gently fold the edges of the dough over the apples, pleating and pinching it to stay in place. Use a pastry brush to lightly coat the top of the tart with egg white. Sprinkle 2 teaspoons sugar over the egg white.