In a small bowl, mix together the steak seasoning, cumin seeds and fennel seeds. Brush the brisket with liquid smoke and then sprinkle both sides with the steak seasoning mixture, making sure to rub it inches Cover loosely with plastic wrap and chill for at least 2 hours or overnight.
Pour the barbecue sauce into a 6-quart or larger Instant Pot. Add the marinated brisket, turning it over to coat both sides. Lock the lid, making sure the valve is set to seal, and cook on high pressure for 75 minutes. Natural release for 15 minutes before manually releasing any residual steam.
Carefully open the lid and transfer the cooked brisket to a cutting board, and let it rest for 10 minutes. Press the sauté button and bring the sauce to a simmer. Cook, stirring often, until the sauce has thickened, about 8 to 10 minutes.
Pour the sauce over the brisket and then thinly slice before serving.
Note: If you want to develop a crust on the brisket, you can place under the broiler for a few minutes after you’ve poured the BBQ sauce over the brisket.