Finely chop the onion. Heat roughly 1-2 tablespoons of olive oil in a large pan over medium heat and sauté the onion for 3-4 minutes until softened.
Add the pressed garlic and cook for 1 minute until fragrant.
Add the diced zucchini, red pepper, and yellow bell pepper. Sauté for 5 minutes until vegetables begin to soften.
Pour in the white wine to deglaze the pan, scraping up any browned bits from the bottom.
Add the tomatoes, cream, and tomato juice. Bring to a boil over medium-high heat.
Reduce heat to low and simmer for 10-15 minutes, stirring occasionally.
Season the sauce with the chopped thyme, salt, and pepper to taste.
While the sauce is simmering, cut the monkfish into medallions roughly 2 cm thick.
Season the fish medallions with salt and pepper.
Heat roughly 1-2 tablespoons of olive oil in a separate frying pan over medium-high heat. Fry the fish medallions for 3-4 minutes on each side until opaque throughout (internal temperature 63°C / 145°F).
Arrange the cooked monkfish medallions on top of the sauce.