Peel the prawns, cut the backs lengthwise and remove the black intestine. Sprinkle with lemon juice and let them sit for half an hour.
Peel the garlic and cut in slices. Heat the oil in a frying pan and sauté the garlic on medium heat. Remove seeds from Spanish pepper, cut in pieces and add to garlic. Cook on low heat.
Dry the prawns and sprinkle with some flour. Turn up the heat under the frying pan and fry the prawns in a few minutes. Server warm with slices of lemon.