1 In a saucepan, brown the onions with a tablespoon of oil, then add the tomato pulp. Simmer for 15 minutes, then add the tuna.
2 In another saucepan, melt the butter over medium heat then whisk in the flour for 3 minutes.
3 Remove from heat, then add the milk gradually while whisking, then put back on the stove and cook until the Béchamel sauce thickens. Season with salt and nutmeg.
4 Wash and cut the zucchini into thin slices.
5 Assembly: Put tomato sauce in the miniature stockpots, then top with slices of zucchini, a lasagna sheet and Béchamel sauce. Repeat this layering, ending with Béchamel sauce and sprinkle with Emmental cheese.
6 Preheat the oven to 180°C (355°F) and bake for 35 minutes.
Tip: You can substitute salmon for the tuna.