Beat the egg and salt in a small mixing bowl with the whisk of the hand mixer until foamy. Mix flour and baking powder and stir in. Add buttermilk while stirring. Let the dough swell for about 10 minutes.
Meanwhile peel the orange and grapefruit so that the white skin is completely removed. Remove the pulp between the parting skins, collecting the juice. Squeeze the parting skins. Stir starch and 2 tablespoons of water until smooth.
Put the juice and cinnamon in a small pot, bring to the boil, stir in the starch and bring to the boil again briefly. Remove from the stove. Heat oil in a pan, add half of the dough and bake until golden on both sides.
Bake the rest of the dough in the same way. Add orange and grapefruit fillets to the bound juice. Dust the pancakes with icing sugar and arrange on a plate with citrus compote. Serve decorated with lemon balm as desired.