Pat salmon filets dry with paper towels and season both sides with salt and pepper.

Melt butter in a large skillet over medium heat; add olive oil. When butter stops sizzling, swirl the skillet to combine. Add 2 or 3 rosemary sprigs to the skillet, to flavor the oil.

Add salmon and cook until salmon is lightly browned and flakes when a fork is gently inserted, about 3 minutes per side. (If salmon filets are thinner than 1 ½ inches, this may take less time.) An instant read thermometer, inserted near the center, should read 145 degrees F (63 degrees C). Remove from the skillet, and keep warm.

To the same skillet with rosemary, add chopped prosciutto, green onion, garlic, red pepper flakes, and lemon zest, and cook for 1 minute or until fragrant.

Add white wine and cook until the liquid evaporates. Add tomatoes and cook, stirring, 2 to 3 minutes. Add spinach and toss in the skillet until bright green and barely wilted, 2 to 3 minutes.

Stir in cream, and season with salt and pepper. Cook until sauce bubbles, about 2 minutes, and remove cooked rosemary sprigs.

Serve salmon on a bed of vegetables and sauce, and drizzle with a little olive oil. Garnish with lemon slices, fresh rosemary sprigs, and toasted pine nuts, if desired.