1/2cupfreshly squeezed orange juice (2-3 oranges with both zest and juice)
1/2cupunsalted butter, cut into small pieces
Cut butter into flour and sugar mixture, either by hand or in a food processor. work in the egg and vanilla extract, and press with your fingers until butter is the size of peas mixed into the flour/sugar, and the whole mixture sticks together easily. Wrap in plastic wrap and form into a disc. Chill in the fridge for 30 minutes and preheat the oven to 350F. Blind bake the shell: crumple parchment paper and fill to the top with dry beans, dry rice or pie weights, and bake in the oven for 20-25 minutes. Let it cool completely.
Prepare a water bath. In a heat-proof bowl on top of boiling water, whisk the orange zest, orange juice, eggs, and sugars for about 10-20 minutes until the mixture thickens and if you dip a spoon into it, and swipe the back of the spoon, the mixture stays separated. Remove the bowl from the water, and add in the cubes of butter in thirds and whisk until it's combined. Let it cool slightly.
Pour the orange curd into the tart shell, and then place in the fridge for at least 4 hours so the curd sets - preferable overnight.
You can follow this recipe for the orange curd for any citrus you like! Lemon, lime, grapefruit, anything!