For this colourful brunch dish, beefsteak tomatoes are stuffed with a spinach, mushroom and Parmesan mixture and topped with an egg before being baked until the tomatoes are tender and the eggs are set.
Preheat oven to 180°C. Lightly coat a 30x23x5-cm baking dish with non-stick cooking spray.
Cut a 3 mm-thick slice off the top of each tomato. Core and seed. Sprinkle inside of tomatoes evenly with 1 tsp salt. Place tomatoes upside down on paper towels to drain.
Wash spinach, letting water cling to the leaves. Place in a very large pan. Cover and cook over medium heat until leaves are wilted, 1 to 2 minutes.
Heat the oil in a large frying pan over medium heat. Add onion; sauté until softened, about 3 minutes. Add mushrooms; sauté until moisture evaporates, 5 minutes. Stir in spinach, breadcrumbs, Parmesan, remaining salt and the pepper.
Pat insides of tomatoes dry with paper towels. Stuff each tomato with spinach mixture. Arrange in baking dish. Crack an egg on top of each tomato cup. Cover loosely with foil and bake until eggs are set, 20 to 25 minutes.