Preheat the oven to 350°F/175°C/Gas Mark 4 (if you have a convection oven, reduce the temperature by about 20° or follow the manufacturer's instructions).
Mix the butter with finely chopped herbs, grated orange zest, and pressed clove garlic. Season to taste with salt and pepper.
Prepare a baking dish, it should be just a little bit bigger than your piece of meat (so that the butter won't burn at the bottom and be spoonable after baking, creating a sauce that you can drizzle over your turkey).
Pour the lemon juice all over turkey tenderloin, season it with salt and pepper on both sides, then spread the butter all over it (the butter won't stick very good to the meat because of the lemon juice, but it doesn't matter, just spread it as good as you can on all sides). If you have time, leave the meat to marinate for 1 hour (or longer, overnight). Take it out of the fridge 30 minutes before you plan on baking it.
Bake for about 37-42 minutes depending on the size of the meat (37 minutes for 12 oz/350g tenderloin and 42 minutes for 15 oz/425g tenderloin). To be sure that the meat is cooked through, check its internal temperature with a meat thermometer. Insert it into the thickest part of the meat, the temperature should be 158°F/70°C (after the resting time it should come to the safe temperature of 165°F/74°C). The baking time may vary depending on the oven.
Let it rest for 10 minutes then cut into slices and serve. Pour the aromatic butter from the baking dish over the meat.
Enjoy!