Little Lime Tarts

1. Preheat oven to 325 degrees (F). Spray 24 mini-muffin cups with baking spray; set aside.
2. For tart shell dough: Cream butter and sugar together in a large bowl with an electric mixer, until fluffy.
3. Mix egg white into the creamed mixture until blended.
4. Add flour and a pinch of salt, mixing until well incorporated.
5. Use a small cookie scoop to scoop dough into the prepared mini-muffin cups.
6. Dip a few fingers into some flour, and press the dough into the cups (across the bottom and up the sides a little) to form a shell for the filling. Repeat with remaining dough. Dust fingers with more flour as needed to keep dough from sticking.
7. Once all of the dough has been shaped into shells, set them aside.
8. For the custard filling: Whisk eggs in a small bowl, until fluffy.
9. Pour sugar, and the melted/cooled butter into the beaten eggs; whisk until well incorporated.
10. Add the lime zest and juice, then whisk until just combined.
11. Pour filling into the tart dough shells, filling them ¾ of the way full.
12. Bake for 20 minutes, or until the edges of the shells are very lightly browned, and filling is set.
13. Remove from oven, and cool in the pan on a wire rack for 5 minutes.
14. Gently run a paring knife along the edges of the tarts to remove them from the pan.
15. Cool completely on the wire rack.
16. To serve, dust with powdered sugar, or a dab of whipped cream or cream cheese frosting, and a sprinkle of citrus zest.
17. Store leftover tarts in an air-tight container in the refrigerator.