In a large skillet, heat oil over medium-high heat. Add onion; cook and stir until tender, 5-7 minutes. Add poblano and red peppers; cook and stir until crisp-tender, 3-4 minutes. Transfer to a greased 5- or 6-qt. slow cooker. Stir in sofrito, tomatoes, 2 tablespoons lime juice, brown sugar and garlic powder.
Toss mushrooms with adobo seasoning; place on top of pepper mixture. Cook, covered, on low until mushrooms are tender, 5-6 hours. Stir in remaining 1 tablespoon lime juice. Serve warm with rice and cilantro.
Portobello Ropa Vieja Tips
How can I make this dish vegetarian?
To make this portobello ropa vieja vegetarian, make your own sofrito versus purchasing store-bought.