Place the lentils in a large saucepan of cold, unsalted water and cook for 30 minutes.
Cut two onions into thick slices and chop the peppers into squares.
Peel the courgettes if necessary. Chop them and the aubergines into cubes.
Separate the cloves of garlic from the head without peeling them. Place all the vegetables in a large bowl. Add a teaspoon of paprika, 50 gr of olive oil and season with salt, pepper and the herbes de Provence. Mix together and transfer to a large baking dish.
Roast in the oven at 200°C for 35 minutes. Stir once or twice during cooking to ensure the vegetables roast evenly.
Once the lentils are cooked, drain them.
Dice the third onion. Fry it lightly in a saucepan with the bacon bits. Once golden, add the lentils, the tomato purée and half a glass of water. Season with salt and pepper. Continue cooking for five minutes.
Serve the lentils and tomatoes nice and hot with the roast vegetables.