Cook the orzo in a large pan of boiling water according to the instructions on the packet. Refresh and reserve.
Make the chilli mayonnaise. Put the mayonnaise, red pepper and red chilli in a food processor or blender and whiz until smooth. Season to taste with salt and pepper and lemon juice.
Combine the crab and orzo in a large salad bowl. Halve the tomatoes and add them to the bowl with the rocket, lemon rind, parsley and capers and mix carefully. Add 2 tablespoons lemon juice and the oil. Season with salt and pepper and serve with a dollop of the chilli mayonnaise.