To make the sweet and sour sauce combine in a small sauce pan the tomato ketchup, sugar, vinegar, sherry and soy sauce. Mix the corn starch with the water, and add as well. Bring the mixture to a soft boil and let simmer for a minute or until thickened and clear looking. Taste. Adjust sugar/vinegar/soy sauce to your liking.
In a wok or large saute pan add the oil and heat over medium high heat. Add the tofu, onion and bell pepper. Fry until tofu is lightly browned and all the vegetables are cooked through.
Add the pineapple. Fry until heated through.
Add the sweet and sour sauce. Stir to mix well. Serve immediately with rice.
Make it healthier
We don't deep-fry the tofu or vegetables, like they do in some recipes, for health and convenience reasons. It tastes way less greasy this way.