Preheat the oven to 180 C / Gas mark 4. Grease a 30x22cm roasting tin, then line the base with greased baking parchment.
Cut the cherries into quarters, place in a sieve and rinse under cold water. Drain well and dry on kitchen paper.
Place the flour, baking powder, margarine, caster sugar, lemon zest, almonds and eggs into a large bowl; beat well for 1 minute. Fold in the cherries. Turn into the tin and sprinkle with the flaked almonds.
Bake in the preheated oven until well risen, golden brown and a skewer inserted into the centre comes out clean, about 40 minutes.
Leave to cool in a tin for 10 minutes then turn out; remove the parchment and finish cooling on a wire rack. Cut into 18 pieces.