Preheat the oven to 375°F (190°C or 180°C for fan ovens).
Prepare the vegetables. Set aside.
Brush a large baking sheet (sheet pan) with a skim of olive oil and put the tenderloins in the oven to brown up a bit.
Cook for ten minutes.
Now add all the vegetables to the pan.
Sprinkle with the pepper, basil, oregano and paprika.
Drizzle the remaining olive oil over the top, and toss the vegetables together around the tenderloins.
Return the pan to the oven.
Bake for 25 minutes, stirring the sausages and vegetables around once, until the vegetables have softened and are beginning to take on some colour.
Remove the sheet pan from the oven and sprinkle the lentils over top of the vegetables.
Drizzle the whole lot with the vinegar and toss to mix and coat.
Return the pan to the oven for 5 minutes. The tenderloin should have reached an internal temperature of at least 145°F (63°C) for medium rare, but I prefer it to be at least 165°C (74°F) for well done.
Remove the baking sheet from the oven and cover with foil. Allow to rest for five minutes while you warm the plates.
Remove the tenderloin from the baking sheet to a cutting board. Cut in slices.
Divide the lentils and vegetables between 4 warmed plates or bowls and serve topped with the sliced tenderloin.
Garnish with flat leaf parsley.