Gently clean the portobello mushrooms with a damp cloth and place them on a baking sheet, gill side up.
In a mixing bowl, combine the halved cherry tomatoes, diced mozzarella, chopped basil, olive oil, garlic powder, salt, and pepper. Mix well until the ingredients are combined.
Spoon the tomato and mozzarella mixture generously into each mushroom cap, packing it slightly to ensure it's filled.
Drizzle the balsamic glaze over the stuffed mushrooms for added flavor.
Bake in the preheated oven for 20-25 minutes, or until the mushrooms are tender and the cheese is melted and bubbly.
Remove the mushrooms from the oven and let them cool for a couple of minutes.
Serve stuffed portobellos warm on a plate, garnished with a handful of arugula if desired.
Notes
Serve warm and garnish with arugula for added freshness.