Heat olive oil in large frying pan over medium heat.
Season salmon steak on both sides with salt and pepper. Sear in hot pan, flesh-side down first, for 5 minutes on each side, or until cooked to your liking. Once cooked, remove from pan and set aside.
In the same pan, add olive oil and fry shrimp for about 2 minutes on each side. Sprinkle with salt, pepper, and lemon juice. Once cooked, remove shrimp from pan and set aside.
Melt butter in the remaining juices left in the pan. Add in garlic and fry until fragrant, about one minute. Saute`onion in the butter. Add sun-dried tomatoes and saute for 1-2 minutes to release their flavor.
Reduce to low heat, add light cream, and bring to a gentle simmer, stirring occasionally. Season with salt and pepper as desired.
Add in spinach leaves and allow to wilt in the sauce.
Add Parmesan cheese. Allow sauce to simmer another minute until cheese melts into the sauce. (For a thicker sauce, add cornstarch to the center of the pan and continue to simmer while quickly stirring until the sauce thickens).
Add salmon and shrimp back into the pan. Sprinkle with parsley and spoon sauce over the top.
Serve. Season to taste.