Cut spaghetti squash in half lengthwise. Remove and discard seeds. Place squash, cut sides down, in a 13- x 9-inch pan, and add water to a depth of 1/2 inch.

Bake at 375° for 45 minutes or until skin is tender and strands may be easily loosened with a fork. Drain and cool slightly. Remove spaghetti-like strands from squash using a fork, and discard squash shells.

Saute onion and garlic in a large nonstick skillet coated with vegetable cooking spray until tender. Stir in tomato and next 4 ingredients; cook until thoroughly heated. Add squash; cook, stirring gently, until thoroughly heated. Makes 8 servings.