Brush halibut filets with olive oil. Season halibut with rub. Heat grill to medium-high heat. Oil the grill with an oiled rag and grill halibut until internal temperature reaches 140ºF.
Bring orange juice, wine, shallots, cream, and vinegar to a simmer in a heavy saucepan. Add cardamom and tarragon and continue to simmer until volume is reduced by half. Reduce heat to low and whisk in butter one piece at a time, lifting pan from heat occasionally to cool sauce. Melt each piece of butter before adding the next. Keep the sauce in a metal bowl over a saucepan of hot water until ready to serve.
To plate, drizzle citrus butter sauce over half the fish until it pools underneath it. Serve with your choice of accompaniment.
OLD BAY® Rub can be used to spice up any white fin fish like tilapia, halibut, flounder, and sole. Serve the fish with fresh guacamole and salsa with tortillas for great fish tacos.
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