Preheat the oven to 375 degrees. Grease five 4-inch mini tart pans.

In a mixing bowl, beat together the crust ingredients.

Press the crust mixture into the mini tart pans.

Bake for 15-20 minutes until the crusts are browned and cooked through. Set aside to cool.

Meanwhile, in a double boiler or a bowl placed inside a pot filled with water, heat the egg yolks, ½ cup sweetener, zest from 2 lemons, juice from 2 lemons, and a pinch of salt. Cook, whisking often, until the mixture thickens.

Once thickened, remove from the heat. Add the butter pieces and stir until smooth and melted.

Fill the cooled crusts with the filling mixture and allow to fully cool before serving.