Heat 1 teaspoon of oil and 1 tablespoon of tamari in large pan over medium-high heat. Stir-fry the tofu for about 10 minutes, or until golden brown on all sides. Transfer to a plate and set aside.
Add the remaining oil to the pan Add the onion and a pinch of sea salt. Cook, stirring frequently for about 5 minutes, until the onion starts to become translucent.
Add the bell peppers and pineapple to the pan. Cook until the peppers have softened, about 10 more minutes, stirring often.
Whisk together the remaining tamari, pineapple juice, water, agave, rice vinegar, cornstarch, tomato paste, garlic chili paste, garlic, and ginger.
Add the tofu back to pan along with the sauce. Gently stir to combine. Cook for about 5 more minutes, until the sauce thickens and is heated throughout.
Remove from the heat and mix in the sesame oil
Top with sliced scallions. Serve over the brown rice.