To segment the grapefruit:
Cut each end of the fruit until you reach the fruit inside. Place on one of the flat sides. Carefully cut down and around, just at the edge of the fruit to remove the skin and expose the flesh of the fruit. Hold the fruit in the palm of one hand over a bowl. Ideally, place a wire mesh strainer on top to catch the seeds and grapefruit segments. Cut into fruit along the white segment to remove the fruit. When all of the flesh has been cut away, squeeze the remaining part to release the juice. Repeat this with the other grapefruit. Discard any seeds that fall out during the process.
Measure the grapefruit juice. Add enough white wine to make one cup of total liquid.
Place a skillet with a lid over high heat. Add the juice. Season the salmon fillets generously with the salt and pepper. Lay the salmon gently in the pan of juice & wine. Reduce the heat to medium-low to create a light simmer in the pan. Cover with the lid. Steam poach for about 6 minutes. Test the salmon by pressing gently, it will feel firm but not hard or check by flaking lightly with a fork. Continue to simmer for a couple more minutes if necessary.
Remove the salmon and turn the stove up to high heat. Place the salmon on a cutting board covered with a lid to keep warm. Boil the juice rapidly over high heat. Stir in the honey, adding more or less depending on the sweetness of the grapefruit and your desired taste. Swirl around the pan and stir until the juice appears slightly thickened. Finish by melting in the butter and tossing in the segments of the fruit.
To serve, place the salmon on plates and drizzle the grapefruit glaze across the top.