Heat a medium pot over medium heat. Add 1 tablespoon extra-virgin olive oil, 1 turn of the pan, and half of the finely chopped onion. Saute 3 minutes, then season with 2 teaspoons cumin, eyeball the measurement in the palm of your hand, and the thyme leaves. Pour in 2 1/2 cups of chicken stock and raise heat to bring to a boil. Add rice and lower heat to simmer when boil resumes. Cover pot tightly. After 12 minutes, stir in black beans and replace cover. Cook another 6 to 7 minutes. Turn off rice and beans, season with salt and stir to combine then let stand until ready to serve. While rice cooks, make plantains with shrimp and the meat.
Preheat a grill pan over high heat. The meat can also be prepared in a hot, large cast iron or nonstick skillet if you do not have a grill pan.
Place flank steak in a shallow dish and drizzle with extra-virgin olive oil to coat – about 2 tablespoons. Mix grill seasoning with 1 tablespoon cumin, eyeball the measurement in your palm. Add the zest of 1 lime to the grill seasoning and cumin. Rub the mixture over the steak evenly. Wash up and cut lime into wedges and reserve. Place the steak on hot grill or in hot pan and cook 4 to 5 minutes, turn and cook 3 minutes longer. Remove from heat and let juices redistribute 5 minutes.
Slit the skins of the plantains from end to end to vent them for microwave cooking. Wrap them each in wax paper, twisting up paper at ends. Microwave the plantains 4 to 5 minutes together or 90 seconds each individually on high.
While plantains and steak cook, place a medium nonstick skillet on the heat over a high flame. Add 2 tablespoons extra-virgin olive oil and the sliced onions. Sear the onions up and heat through, but leave a bite to them. Place on a platter and cover with foil to reserve heat. Return pan to stove and reduce heat to between medium high and medium. Add 2 tablespoons extra, 2 turns of the pan, and the remaining finely chopped onion, the bell pepper, garlic and shrimp. Season with salt and pepper and add the zest of 1 lemon. Cook until shrimp are firm and peppers begin to soften, 4 minutes or so. Add the juice of 1/2 lemon, the tomato sauce and parsley. Turn off heat.
Peel and mash the steaming hot plantains with remaining 1/2 cup chicken stock and a drizzle of extra-virgin olive oil. Season the plantains with salt and pile on platter or dinner plates then top with garlicky shrimp and tomatoes. Very thinly slice the cooked steak on an angle, working against the grain. Squeeze lime juice over the meat and arrange over the cooked sliced onions on serving platter. Fluff up rice and black beans a bit, transfer them to a bowl and pass at table.