Preheat the oven to 160 °C / 320 °F. If you are using a fan-assisted oven, preheat it to 145 °C / 290 °F. Line a baking sheet with parchment paper. Pat dry the fillet using paper towels and check if there are maybe any leftover pin bones in the fillet. If you find any, remove them using fish tweezers. Place the salmon fillet skin side down on the prepared baking sheet. Season with salt and pepper and drizzle with olive oil. Arrange four lemon slices on top.
bake and serve
Transfer the fish into the oven and bake for 20 - 25 minutes at 160 °C / 320 °F or in a fan-assisted oven at 145 °C / 290 °F, or until a thermometer inserted into the thickest part of the fish registers 48°C - 50°C (118°F - 122°F). The salmon fillet is perfectly baked when it's soft, flaky, and separates easily with a fork. Divide between four plates and serve.