Heat the cumin and coriander seeds in a large cast-iron skillet over medium heat until toasted, about 3 minutes. Transfer the seeds to a food processor. Raise the heat under the skillet to medium-high.
When the skillet is smoking hot, season the steak generously with salt and pepper and put in the skillet. Cook, turning once, until nicely browned, 4 to 5 minutes per side for medium-rare.
Meanwhile, add the garlic and 1/2 teaspoon salt to the food processor. Pulse, scraping the bowl occasionally, until the garlic is minced and the cumin and coriander are cracked. Add the cilantro, parsley, and paprika. Pulse until the herbs are very finely chopped. Add the oil and puree until smooth, scraping the bowl as needed.
Let the steak rest on a cutting board for 5 minutes. Cut into thin slices and divide among serving plates.
Stir the lemon juice into the sauce, then season to taste with salt and pepper. Spoon all over the steak and serve.
Recipe by Genevieve Ko.