Preheat the oven to 200ºF.

Combine all the seasonings for the steak in a small bowl. Sprinkle the beef on all sides with the seasonings and then rub with the coconut aminos. Place steaks on a wire rack set into a rimmed baking sheet. Bake at 200ºF until the internal temperature of the steak is 115ºF, about 20-45 minutes for medium-rare. This will vary depending on the thickness of your steak (thicker steaks will take longer) and oven conditions so check its internal temperature (see note for temperatures).

While the steak cooks, prepare the vegetables. Microwave the Brussels sprouts in a microwave-safe bowl until they are just fork-tender, about 4-8 minutes, depending on your microwave’s power (check at 4 minutes). Alternatively, you can steam them in a steamer basket on the stovetop for about 5 minutes if you prefer.

Heat a large nonstick pan over medium-high heat and add the oil along with the bell pepper, onion, and mushrooms. Cook, stirring occasionally until the onions are soft and translucent and the mushrooms have released their liquid, about 5-8 minutes. Add the garlic and cook for another minute, until fragrant. Add in the steamed Brussels sprouts and turn the heat to high. Cook until lightly charred, about 5 minutes. Turn off the heat and add the spinach, stirring to incorporate it - the residual heat will wilt the leaves. Stir in parsley and cilantro, season to taste with salt. Serve along with beef.