Combine apricots and almond liqueur (or orange juice) in a large bowl. Grate 2 teaspoons zest from the lemon and set aside. Juice the lemon and stir 2 teaspoons of the juice into the apricots. Let stand for at least 1 hour.
Preheat oven to 350°F. Coat a 10-inch round baking dish, such as a ceramic quiche dish, or oval casserole with cooking spray. Sprinkle 1 tablespoon sugar evenly over the bottom. Drain the apricots (reserving syrup) and arrange in the baking dish.
Combine eggs, egg white and the remaining 1/3 cup sugar in a medium bowl. Beat with an electric mixer on medium speed until pale yellow. Add milk, flour, almond extract, salt, the reserved lemon zest and the reserved syrup; beat well to blend. Pour the batter over the apricots; sprinkle with almonds. e the clafouti until puffed and golden, 45 to 55 minutes. Let cool for about 20 minutes. Sprinkle with confectioners' sugar and serve warm.