Mix sea salt with sugar, zest, peppercorns and rosemary. Sprinkle the tenderloin with this mixture and refrigerate for 1 hour. Cut the pumpkin into cubes, fry in olive oil, add a little water and simmer until softened. Drain water, salt, pepper. Add butter and puree in a blender. Peel the tenderloin from salt, wrap in foil and bake in a hot frying pan over medium heat for 10-15 minutes. Cool slightly, remove from foil and cut into medallions. To serve, place on a pillow of the remaining salt, put pumpkin puree next to it.