For the cornmeal polenta, boil the vegetable soup with the oil, stir in the cornmeal and cook, stirring constantly, until a solid mass is formed.
Spread the polenta 1-2 cm thick on a baking sheet and let it cool, then cut it out with a cookie cutter and fry it in a little oil until crispy on both sides.
For the avocado-melon salsa, break the rice cakes into small pieces. Peel the watermelon and avocado and cut the flesh into small cubes. Mix with the remaining ingredients and season the salsa with lime juice, salt and pepper.
Arrange the patties on warmed plates and garnish with the salsa.