In a 2- to 3-quart pan over high heat, bring 3 1/2 cups water and the rice to a boil. Reduce heat to medium-high and cook, uncovered, until most of the water is absorbed, 7 to 10 minutes. Turn heat to low, cover, and cook until rice is tender to bite, 10 to 15 minutes longer.
Meanwhile, rinse pork and pat dry; cut into 3-inch-long strips 1 inch wide and 1/4 inch thick. In a small bowl, mix pork with 1 tablespoon soy sauce.
Peel onion and cut lengthwise into 1/4-inch-wide slivers. Rinse, stem, and seed bell pepper; cut lengthwise into 1/4-inch-wide slivers about 3 inches long.
Drain pineapple juice into a 1-cup glass measure. Add enough water to make 2/3 cup. Stir in remaining 1 tablespoon soy sauce, catsup, cornstarch, sugar, vinegar, and cayenne.
Pour 1/2 teaspoon oil into a 12-inch nonstick frying pan or 14-inch wok over high heat. When oil ripples when pan is tilted, add onion, bell pepper, ginger, and garlic. Stir often until bell pepper is tender-crisp to bite, 2 to 3 minutes. Pour from pan into a serving bowl.
Add remaining 1 teaspoon oil and the pork to pan; stir often until pork is no longer pink in the center (cut to test), 4 to 5 minutes. Return onion mixture to pan and add pineapple. Stir the pineapple juice mixture and add to pan. Stir until sauce boils and thickens, about 1 minute. Add salt to taste. Pour into a serving bowl and serve with hot cooked rice.