Make the sweetbreads disgorge for about 2 h in a salad bowl filled with slightly vinegary cold water, changing the water if need be, until they are nice and white.
Blanch for about 5 min at low boil in a pan of water, starting it cold. Refresh under cold water and drain on absorbing paper.
Delicately get rid of the small skins and cut into regular pieces.
Heat up a pan with oil inside, colour the sweetbreads for a few minutes on a high flame, salt and pepper. Set aside and keep warm.
Peel the rhubarb and cut into pieces. Blanch for 1 min in boiling water. Drain and quickly run cold water over. Dry with absorbing paper.
Heat up a pan with butter, colour the rhubarb. Add the honey and the cardamom, cook for 1 min on low flame, add the glazed tomatoes and the rosemary, mix.
Serve the panned lamb sweetbreads with the rhubarb and tomatoes..