Pat the salmon filets dry with paper towels, and then sprinkle each side with salt, black pepper, and garlic powder. Put the flour in a shallow bowl, then dredge the salmon filets in it. Shake off the excess flour.
In a large frying pan, melt one tablespoon of butter on medium-high heat. Once the pan is hot, add the salmon filets and cover with a lid. Cook for about 4 minutes (until golden), then flip the salmon filets and cook covered for another 3-4 minutes (until golden and cooked through**). Move the salmon to a plate and cover with tin foil.
In the same warm frying pan (heat off), melt two tablespoons of butter. Add the minced garlic, thyme, oregano, salt, and black pepper, and saute on low heat and stir for one minute.
Add the chicken broth, white wine vinegar, and lemon juice. Mix well, then turn the heat to high and bring to a boil.
Mix the two tablespoons of cornstarch with two tablespoons of cold water in a small bowl. Add the mixture to the frying pan, and whisk well. It may get a little bit clumpy, but don't worry about that.
Turn the heat down to low, and whisk in the heavy cream until smooth. Then, mix in the capers and fresh parsley.
Mix in the cooked fettuccine and serve, topped with the cooked salmon. Squeeze some fresh lemon juice on top (optional), and enjoy!