1.

Place onions in a small bowl and cover with cold water. Set aside. Combine tomatoes and peppers in a colander set over a bowl and season with 1/2 teaspoon kosher salt and a few grinds black pepper. Allow to rest at room temperature for 20 minutes. You should end up with about 2 tablespoons juice in the bowl. If excess juice is collected, discard all but 2 tablespoons.