First you marinate half-inch thick tuna steaks in a mixture of dijon mustard, and orange juice, with pinches of tarragon, salt, and cayenne. While the tuna is soaking up flavor, sauté an onion in half-inch wedges and a small red bell pepper in half-inch strips in a bitter butter. When the onion starts to brown on the edges, stir a slog of balsamic vinegar with a tiny dab of honey. Then add orange juice and white wine. Lay the tuna steaks on top of this mixture, sprinkle with a bit of salt and cayenne, close the pressure cooker, and put it over high heat.
The instructions say to cook at pressure for 2-1/2 minutes for a slight pink center or 3 minutes for full cooked. Our steaks were fully cooked at 2-1/2 minutes, which is a shame, since we both like our tuna, not even pink, but red in the center.