Chop the rhubarb and strawberries roughly. Place them in a bowl with the lemon zest and brown sugar. Mix and leave to stand while you make the crumble.
Mix gluten-free flour, white sugar, almonds and cold butter.
Crumble the mixture until you have a crumble batter.
Place the strawberry-rhubarb mixture in the bottom of the ramekins and sprinkle with crumble.