Heat olive oil in a medium saucepan over medium heat. Sauté the onions in oil until tender and beginning to brown, 6-8 minutes. Stir in the garlic and sauté for 1 minutes. Add the tomato paste, salt, ground mustard, paprika, cloves, allspice, and crushed red pepper. Stir with a wooden spoon for 1 minute, until fragrant. Add the brown sugar, vinegar, and tomatoes. Simmer over low heat, stirring occasionally, for 45 minutes, until the tomato mixture has thickened.