Warm a large skillet over medium heat and drizzle in the olive oil.
While the oil heats, pat dry the salmon fillets with paper towels, then season both sides with salt and pepper.
Place the salmon fillets skin side down in the hot skillet in a single layer and cook for 3 minutes on each side until just cooked; then transfer them to a plate and keep warm.
In the same skillet at medium heat, add the chopped onion and garlic, stirring constantly until the onion turns translucent, about 3 minutes.
Sprinkle the flour over the onion and garlic and stir continuously for 2 minutes to cook the flour.
Add the dried oregano, thyme, smoked paprika, and crushed red pepper, quickly stirring to combine.
Pour in the milk and vegetable broth, stirring gently for a few minutes until the sauce starts to thicken and become creamy.
Mix in the chopped sundried tomatoes, grated Manchego cheese, fresh basil, and lemon juice.
Return the salmon fillets to the skillet, nestling them into the sauce, lower the heat, and let everything simmer for 2 to 3 minutes until the salmon is heated through.
Serve the salmon and creamy sauce directly from the pan, garnished with lemon wedges and chopped parsley.