Mix minced garlic, soy sauce, peanut butter, rice wine vinegar, ginger, and sriracha in a small bowl. Set aside.
Heat sesame oil or a little vegetable broth in a pan over medium high heat.
Add diced onion and red pepper to the pan. Cook until the onions start to become translucent and peppers soften, about 3 minutes.
Turn the stove temperature down to a medium low. Add the diced tempeh, pineapple, and sauce mix to the pan. Stir and cook until everything is hot and sauce is fragrant, about another 3 minutes.
Serve in leaves of lettuce. Garnish with cilantro and more sriracha (if you want it hot).