Preheat oven to 450º.
Combine tomato wedges and oil on a baking sheet lined with foil, tossing well to coat. Bake at 450º for 15 minutes or until tender and lightly browned.
Melt butter in a large saucepan over medium-high heat. Add onion, and sauté 3 minutes. Add couscous, curry, salt, and garlic; sauté for 3 minutes. Add tomato wedges and stock, and bring to a boil. Reduce heat, and simmer 7 minutes or until the couscous is almost tender. Stir in spinach, and cook for 2 minutes or just until spinach wilts.