Prepare Ingredients: If using fresh corn, cook the kernels by boiling or grilling, then let them cool. If using frozen corn, thaw completely.
Combine Ingredients: In a large bowl, mix together the corn, diced tomatoes, red onion, jalapeño, and cilantro.
Add Seasonings: Stir in the lime juice, garlic powder, cumin (if using), salt, and black pepper. Adjust seasoning to taste.
Chill (Optional): For best flavor, cover the salsa and refrigerate for 15-30 minutes before serving.
Serve: Serve with tortilla chips, tacos, or as a topping for grilled chicken, fish, or salads.