Preheat oven to 300 degrees F.
In a bowl, combine melted butter with the garlic, shallots, fennel seeds, zests, tarragon, black pepper, and lemony thyme.
Brush a ceramic baking dish with olive oil. Lightly season the salmon fillet with kosher salt. Spread half of the seasoning mixture on the skinned side of the fish.
Place skinned side down in baking dish and top with remaining seasoning mixture.
Sprinkle with cayenne pepper.
Let the salmon sit at room temperature for 20 minutes.
Carefully pour the orange juice into the baking dish and cover the dish tightly with foil.
Bake the salmon for 35 minutes, until the fish is barely opaque in the center.