Cut out almost in 24 pieces of regular size. Peel the onions and cut them in four. Peel the zucchini and cut into eight.
Thread the cubes of meat on wooden skewers (preferably place the largest pieces at the ends) alternating meat, zucchini and onions.
Mix the olive oil, the juice and grated rind of the lemon as well as the thyme leaves in a deep dish. Put the skewers to marinate in this preparation. Let them rest for 30 minutes in the fridge, turning them over several times.
Drain the skewers and reserve the marinade. Place them on a grilling plate on a deep dish and cook for 12 to 14 minutes at 700 W, basting with the marinade and turning the skewers several times during cooking. Salt, pepper, drain the juice in a bowl, cover and let the skewers rest about 3 minutes.
Mix the Maïzena in a little water, pour this mixture into the cooking juices and add the rest of the marinade. Mix well and cook for 2 minutes at 600 W, stirring regularly.
Serve the skewers topped with sauce, and accompany with a fragrant rice or a green salad.