Food processor: in the bowl of a food processor mix flour with coconut and sugar.
Add cold butter and pulse a few times until the butter is the size of peas.
Add yolk and pulse just until it starts to come together. Don’t let it become a ball of dough.
If the dough is too dry add a tablespoon of water, but only if necessary.
By hand: in a large bowl mix flour, coconut, and sugar.
Add butter and mix with a dough cutter or with your hands, breaking the butter pieces until they are the size of peas. Be careful not to let the butter start to melt. If that happens, pop the bowl for ten minutes in the fridge before continuing.
Add yolk and mix with a fork until it starts to come together.
If the dough is too dry add a tablespoon of water, but only if necessary.
For both methods: either way, you mix it, turn the dough onto the clean counter.
Gather it together and give it some turns until no dry spots are left. It should be soft but don’t overdo it. Just until you have a ball.
Wrap in plastic and refrigerate for 1 hour or up to 1 day.
You will use an 8-inch tart pan with removable bottom.