First off, line a baking sheet with foil. Cut 6 medium sized tomatoes in 1-inch pieces and arrange on the baking sheet in a single layer. Also cut a small red onion into inch sized bits and add to the baking sheet alongwith 4-5 peeled garlic cloves. Drizzle a tbsp of olive oil on the tomatoes and sprinkle a tbsp of herbs de provence all over. This goes into the oven preheated to 220C for 45 minutes.
By this time, your tomatoes and onion should be softened so everything goes from the baking tray to a thick bottomed pan. Mash them lightly with the back of a spoon, then add 2 tbsp of tomato paste and a tbsp of white wine vinegar. Let simmer on a low heat for 15-20 minutes. Finally, add salt to taste and a tsp of olive oil, mix everything in and take the pan off the heat.
Let it cool down a bit, then pulse it in the food processor until you get to a consistency you like. This is good with pasta, and makes a good topping for pizzas too.