Pat the flank steak dry with a paper towel to ensure a proper sear.
In a small bowl, combine the cumin, chili powder, sea salt, and black pepper.
Rub the spice blend evenly over both sides of the steak.
Heat the olive oil in a large cast-iron skillet over medium-high heat until shimmering.
Place the steak in the skillet and sear for 4 minutes per side for medium-rare, or until it reaches your desired doneness.
Remove the steak from the pan and let it rest on a cutting board for at least 5 minutes.
In the same skillet, add the sliced bell peppers and red onions, sautéing for 5-6 minutes until tender-crisp and slightly charred.
While the vegetables cook, warm the black beans in a small saucepan or microwave.
Slice the rested steak against the grain into thin strips.
Assemble the bowl by layering the black beans, sautéed vegetables, and sliced steak.
Finish with a squeeze of lime juice, a dollop of Greek yogurt, and a sprinkle of fresh cilantro.