Combine mangoes, tomatoes, and red onion in a bowl.
Add vinegar, sautéed shrimp paste, a drizzle of extra-virgin olive oil, and some salt and pepper to taste.
Gently toss them together. If the mangoes aren't sweet, you can add honey or sugar to balance the flavors and add a touch of sweetness. Adjust the amount according to your taste.
Garnish with fresh cilantro, chives, or scallions.
Notes
Mangoes: You can use tart green carabao mangoes or Indian mangoes in the Philippines. If you are in the US, look for the firm Keitt or Haden mango variety.
Sautéed shrimp paste: An umami-rich condiment made with fermented shrimp. Be sure to use the cooked, sautéed shrimp paste, not the raw/pink variety. You can use fish sauce as a substitute.