Heat oil in sauté pan over medium heat and cook shallots until just beginning to brown, about 5 minutes. Add garlic and continue cooking for 1 minute. Stir in sugar, red pepper flakes, vinegar, pepper, oregano, and tomatoes. Reduce heat and simmer mixture on low until thick like jam, 20 to 30 minutes. Cool and fold in olives and capers. Can be stored for up to two weeks, tightly covered, in the refrigerator.