Preheat oven to 350F. Line a baking pan with parchment paper.
Cut a slit through the middle of each salmon filet, about 2/3rd of the way through. Set aside.
In a large bowl, stir together the crabmeat if using, chopped mushrooms, 8 oz. of Tzatziki with Feta Dip & Spread, lemon juice, chopped scallions if using, chopped dill or parsley, and breadcrumbs.
Stuff each open salmon slit with an equal amount of the filling, mounding on top of filet. Drizzle the salmon with olive oil, then season with salt and black pepper.
Bake for 20-30 minutes, or until the salmon flakes easily with a fork.
Add the spinach and toss with the garlic. Stir until spinach is just wilted, about 1-2 minutes. Season with salt and black pepper. Serve immediately with the cooked salmon.