Step 1Set up a charcoal grill for direct heat over three-quarters of the grill or heat three-quarters of the burners of a gas grill on medium-high. Keep the remaining quarter of the grill unheated. (Alternatively, heat a large skillet or grill pan on a stove-top over medium-high heat.)
Step 2Put the sake, soy sauce and mirin in a heavy-duty, small saucepan. Put the saucepan on the hot part of the grill and bring the mixture to a boil. Wearing an oven mitt, move the saucepan to the part of the grill that will keep the mixture at a steady simmer, either over the unheated part of the grill or between the heated and unheated parts. If working on a stove-top, bring the mixture to a boil over high heat, then reduce the heat to maintain a simmer. In either setup, simmer until syrupy, about 10 minutes.
Step 3While the sauce simmers, rub the salmon all over with 1 tablespoon olive oil, sprinkle with salt and place flesh-side down on the hot part of the grill. Toss the broccoli rabe with the remaining 1 tablespoon olive oil, sprinkle with salt and arrange on the hot grill grate in a single layer. Cook everything together, turning the broccoli rabe once, until the salmon releases easily from the grill grate and the broccoli rabe is charred and tender, about 5 minutes. Transfer the broccoli rabe to serving plates and carefully flip the salmon. Brush some teriyaki sauce on the salmon and continue grilling, brushing on more sauce once more, until the fish is almost cooked through, 3 to 5 minutes longer. A thin-bladed knife or metal cake tester should slide through the thickest part of the fish with little resistance.
Step 4Transfer the salmon to the plates with the broccoli rabe. Drizzle the teriyaki sauce all over, sprinkle with togarashi and sesame seeds, and serve with lemon wedges.