For the meatloaf:
1-1/4 lb ground turkey (I use 93% fat-free)
1 large egg
1/4 cup crumbled feta cheese
1/2 cup plain or seasoned dry bread crumbs
1/4 cup caramelized onions*
2 cups spinach leaves, chopped
4 tsp Dijon mustard
1 tsp thyme
1/2 tsp fresh black pepper
1/2 tsp kosher salt
For the sauce:
1/2 cup mayonnaise
Zest of 1/2 lemon
Fresh black pepper, to taste
Small potato rolls or other slider buns
Romaine lettuce leaves
Preheat oven to 400°F. Line a rimmed baking sheet with aluminum foil, and set aside.
In a large mixing bowl, combine all of the meatloaf ingredients. Mix with your hands just until everything comes together; do not overmix. Transfer to the prepared baking sheet, and form into a loaf shape.
Bake at 400F for 55-60 minutes. Take the meatloaf's temperature at 55 minutes with an instant-read thermometer; the temperature should read 160°F. If it doesn't, return to the oven for an additional 5 minutes.
While the meat is cooking, combine the sauce ingredients in a small bowl, and set aside.
Remove the meatloaf from the oven and let it sit for 10 minutes before slicing with a serrated knife.
To serve as sliders, set out as many small rolls as you wish. Place a piece of crisp lettuce on the bottom half, and slather the lemon sauce on the top. Cut pieces of meatloaf to fit. Serve warm, at room temperature, or cold.