Heat 1 tablespoon of the oil in a cast-iron or nonstick skillet over medium heat. Add the onion and bell pepper and sauté until softened, 5 to 7 minutes. Add the garlic and sauté just until fragrant, about 30 seconds. Let cool to room temperature.
In a medium saucepan, bring 1/2 inch of water to a simmer over medium heat. Add the edamame and season lightly with salt and pepper. Cover and cook until just tender and heated through, about 4 minutes. Drain well and let cool to room temperature.
Add the onion mixture, corn, tomatoes, Sriracha, cilantro, vinegar, liquid aminos, and remaining tablespoon of oil and mix well. Season with salt and pepper to taste.
Cover and refrigerate for at least 30 minutes. Taste just before serving and add more vinegar or Sriracha if desired. Serve garnished with cilantro sprigs.