In an iron skillet (8 to 10 inches wide), heat 2 tablespoons olive oil on a medium flame. Add the garlic and fry for a few seconds, then add the onions and cook till lightly browned.
In a separate pan on medium heat, add the remaining olive oil and cook the zucchini and bell pepper till lightly browned. I like doing this for a nice caramelised flavour, and because my skillet is small and won't fit all the veggies at once, but feel free to cook the zucchini and bell pepper with the onions.
To the mushrooms, add the chopped tomatoes and three-fourths of the cherry tomatoes. Cook till the tomatoes have softened and begun to release their juices. Then add the seasonings and stir well.
Add the red wine, then the cooked zucchini and bell pepper. Stir in the basil. Mix very well, then cover for 3 to 4 minutes until the liquid is bubbling and slightly thicker.
Meanwhile, preheat the oven to 220 C.
Place the halloumi slices on the cooked veggies, and add the rest of the cherry tomatoes on top as well, so that they become nice and blistery in the oven.
Bake for 15 to 20 minutes until the cheese is browned, the sauce has thickened further and the veggies are sticking to the edges of the pan slightly. Remember that the mushrooms and tomatoes both release water as they bake, so the sauce will always be on the thinner side.
Let the skillet stand for 10 minutes, then sprinkle on more fresh basil and serve with crusty, extra toasty bread!