Prep and drain the tomatoes. Dice the tomatoes into 1/4-inch pieces and place in a fine-mesh sieve or colander over a bowl. Let them drain while you prep everything else.
Marinate the onions and garlic. Juice the limes into a large mixing bowl. Dice the red onion to match the tomatoes, then finely grate the garlic with a Microplane (or mince it finely with a sharp knife). Add both to the lime juice, stir, and set aside.
Prep the beans and corn. Rinse and drain the black beans and add to the large mixing bowl along with the onions and garlic. If using canned corn, rinse and drain it too. If using frozen, thaw it first. Sauté the corn kernels in a dry skillet over medium heat until lightly browned. Allow to cool to room temperature before adding to the large bowl.
Dice the peppers. Dice the bell pepper and jalapenos to match the tomatoes, removing the white membranes and seeds. For a spicier salsa, keep some or all of the jalapeno seeds. Add the peppers to the large bowl.
Combine and season. Add the drained tomatoes and spices - chili powder, cumin, red pepper flakes, and kosher salt to the large bowl.
Chop and add the cilantro. Finely chop the cilantro, including any tender stems and add to the bowl.
Rest, taste, and serve. Let the salsa sit for at least 10 minutes so the flavors meld. Taste and adjust with more salt or lime juice, store in the refrigerator until ready to serve. Enjoy with tortilla chips for dipping. Enjoy!