Line a 12-section muffin tray with paper muffin cases. Put the tea, ground almonds and sugar in a food processor and process briefly until combined. Turn into a bowl and stir in the flour, baking powder, lemon rind and sultanas.
Mix together the melted butter, eggs and buttermilk in a separate bowl and add to the flour mixture. Use a large metal spoon to stir the ingredients together until only just combined. Divide the muffin mixture between the paper cases.
Bake in a preheated oven, 220°C (425°F), Gas Mark 7, for 15–18 minutes or until risen and pale golden. Serve warm, split and buttered.