Beat the margarine, sugar, eggs, flour and lemon rind in a mixing bowl or a food processor until smooth.
Divide the mixture evenly among foil cake cases arranged in a 12-hole deep muffin tin and spread the surfaces level. Bake in a preheated oven, 180°C (350°F), Gas Mark 4, for 15–18 minutes until golden and the cakes spring back when gently pressed with a fingertip. Leave to cool in the tin.
Mix the icing sugar with 4–5 teaspoons of the lemon juice to make a smooth thick spreadable paste. Trim the tops of the cakes level if needed. Spoon half the icing over half the cakes and ease into a smooth layer with a wetted round-bladed knife.
Colour the remaining icing pale yellow or pink and spoon it over the remaining cakes. Decorate with homemade pastel-coloured flowers stamped out from ready-to-roll icing or use shop-bought sugar flowers. Leave to harden for 30 minutes. Store in an airtight tin for up to 3 days.