Preheat oven to 325F

Combine ½ cup butter and ¼ cup sugar in a mixing bowl and then add 1 cup flour until you get a soft crumbly consistency.

Evenly divide dough between 12 muffin cups and smash down with a cup that is equally sized to the muffin cups.

Bake muffin tin at 325F for 10 minutes until the “crusts” puff up slightly and cooked through, though not very browned.

While the crusts bake, make the lemon filling. Combine the 1 cup sugar, ½ cup flour, 2 Tbs melted butter and 5 eggs in a large mixing bowl and vigorously whisk, adding air to the eggs.

Once the crusts are done baking, take them out of the oven to cool for at least five minutes.

Add in the lemon and tangelo juices and the lemon and tangelo zests to the egg mixture then pour evenly into the 12 muffin tin cups filled with crusts.

Place the tarts into the oven at 325F for 8 minutes, then rotate the pan and bake an additional 4 minutes, rotating the pan every 2 minutes until the centers of the tarts no longer jiggle when moved.

Remove from oven and allow to cool on the counter for 10 minutes then place the pan uncovered into the freezer to stop the cooking process and preserve the soft, gooey center.

Keep in the freezer at least 20 minutes then transfer to the fridge until ready to serve.

When ready to serve, pop the tarts out of the pan by running a knife along the edge of each tart.