Preheat oven to 400degreesF. Grease a 3-quart baking dish. Combine bread and 1 Tbsp oil on a baking sheet. Toss to combine, spreading in a single layer. Bake 10 minutes or until toasted and golden brown; set aside. In a large skillet, heat remaining 1 Tbsp oil over medium-high heat. Add sausage and onion. Cook 8-10 minutes or until sausage is cooked through and onion is translucent, using a wooden spoon to break up sausage into small pieces. Stir in spinach; cook 2-3 minutes or until wilted. Add tomatoes; cook 2 minutes. Season with salt and pepper; set aside. In a medium bowl, beat eggs, milk, ¼ tsp salt and ¼ tsp pepper until frothy. Spread toasted bread cubes in a single layer in bottom of prepared baking dish. Top with sausage mixture. Pour egg mixture over top so it covers entire casserole. Cool to room temperature, cover and refrigerate at least 4 hours and up to overnight. When ready to serve, preheat oven to 350degreesF. Sprinkle casserole with cheese. Bake, uncovered, 1 hour or until set. Cool 10-15 minutes before serving.