Firs make the grilled tomatoes. Put them in a tray. Mix the balsamic with the oil and garlic, pour over the tomatoes. Put the tray in the oven and grill or roast them for a few minutes, until tender.
Meanwhile, chop the onion and mince the garlic. Cut the bell pepper into small slices.
Drain and put the drained beans and corn into a large mixing bowl, then add the bell pepper and onion.
Mix the oil, mustard, lemon juice, spices and garlic. Season with salt and pepper and pour over the salad. Combine well.
Cut the avocado in half, remove the stone, then cut the flesh into chunks. Add these to the salad, combine well.
Finally, add the tomatoes (without the vine) and the jus to the salad and combine gently.