Chop onion and bell peppers into bite size pieces. Saute in a pan with your olive oil until slightly softened for about 8-10 minutes. Then add green onion and garlic and cook for 2 more minutes. Remove from heat.
Cut tofu into bite size pieces. Lay in a single layer on a cheese cloth or paper towels. Very gently press down to remove as much water out of the tofu as you can without breaking down the pieces.
In a separate sauce pan add all ingredients for the sauce EXCEPT for the cornstarch water mix. Heat on medium high heat until it bubbles, stirring constantly. In a small dish whisk together cornstarch and water until smooth, add in and stir until it is as thick as you'd like. Remove from heat.
Add tofu in with veggies and pour warm sweet and sour sauce over the top of everything. Gently fold together to warm all ingredients. Serve with rice topped with sesame seeds and diced green onions.