Cut the tomatoes into small cubes. Finely chop the spring onions. Mix both with olive oil, lemon juice, cayenne pepper, salt and pepper.
Cut the bread into cubes and allow to soak in the milk. As soon as the bread is soaked through, squeeze out gently and pick to pieces with a fork.
Put the spinach in a bowl and pour in plenty of boiling water. Allow to stand for 1-2 minutes, sieve and plunge in gold water. Squeeze out the spinach well and roughly chop.
Cut away four thin slices of approx. 25g each from the Gruyère AOP. Finely grate the remaining Gruyère AOP and add to the bread, spinach, eggs and herbs in a bowl.
Press in the garlic, and add nutmeg, salt and pepper to taste. Mix everything together well.
Shape eight burgers from the mixture and turn in the breadcrumbs. Fry in frying butter on both sides for je 3-5 minutes each. Top four of the burgers with tomato sauce and Gruyère AOP and cover with the remaining burgers.