Preheat your oven to 350°F (175°C) and grease a muffin tin or line with parchment liners.

In a mixing bowl, cream together the softened butter and ¼ cup of sugar until light and fluffy.

Gradually mix in the flour and a pinch of salt until a crumbly dough forms.

Press the dough firmly into the muffin tin cups, aiming for a thickness of about ¼ inch.

In a small saucepan, combine chopped rhubarb, 2 tablespoons of sugar, and lemon juice.

Cook over medium heat for 5–7 minutes until rhubarb softens, then let cool slightly.

Whisk the egg whites in a separate bowl until frothy, then stir in ½ cup of sugar, vanilla, salt, and shredded coconut.

Spoon a teaspoon of the rhubarb mixture over each crust in the muffin tin.

Top each filled crust with the coconut mixture, gently pressing it down.

Bake in the preheated oven for 20–25 minutes until the tops are golden brown.

Let the tarts cool completely in the muffin tin before removing.