Boil a pot of seasoned water, you want the water to be as salty as seawater.
If you're going to add bacon, fry them up first. If you are using salmon, bake it to your preference.
Heat up a bit of oil and sweat the onion and garlic. Add the thawed spinach (make sure you've pressed out all moisture). Add the cooked spaghetti and optionally the bacon or salmon.
Turn off the heat and mix in the pesto and creme fraiche. Season with salt, pepper and chili flakes. Serve with grated mature cheese.