1. Preheat oven to 450°.
2. Place first 3 ingredients in a 12-inch ovenproof nonstick skillet, and cook over medium-high heat 7 minutes or until sausage is browned, stirring to crumble. Stir in hash browns, salt, and pepper; cook over medium-high heat 3 minutes.
3. Combine milk and egg substitute, stirring with a whisk. Stir in 1 cup cheese; pour evenly over hash brown mixture. Sprinkle with remaining 1/2 cup cheese.
4. Bake at 450° for 18 minutes or until set and top begins to brown. Top with sliced tomato.