Cut off the top and bottom of 2 oranges. Using a small, sharp knife, cut away the peel and white pith from the oranges, following the curve of the oranges from top to bottom.
Working over a bowl and holding 1 orange in your hand, make 2 cuts within the membrane on either side of a segment, then lift the segment out of the membrane and place it in the bowl. Repeat to remove all the segments from both oranges.
Squeeze the membranes to release as much juice as possible.
Transfer the accumulated juices to a 2-cup measuring cup. Set the segments aside. Squeeze the remaining 6 oranges into the measuring cup until you have 2 cups of juice total.
Bring the orange juice to a simmer in a medium saucepan over medium-high heat and reduce until the juice has a syrupy consistency. Remove from the heat and keep warm.
Meanwhile, steam the broccolini just until vibrant green, about 2 minutes. Remove the broccolini and cool.
Drizzle the broccolini with olive oil and season to taste with salt and pepper.
Grill the broccolini until it is crisp-tender and slightly charred, turning as needed, about 5 minutes.
Heat 1 tablespoon of olive oil in a heavy large nonstick skillet over medium-high heat. Add the salmon fillets and cook until golden brown on the outside and opaque around the sides but not quite opaque in the center, about 3 minutes per side.
Transfer the salmon fillets to a plate and let rest for 2 minutes.
Divide the broccolini among 4 serving plates. Place the salmon atop of the broccolini. Drizzle the warm orange reduction over and around the salmon and garnish with the orange segments.