While the skillet warms up, peel and small dice the onion into ¼-inch pieces; transfer to a small bowl.
1 medium yellow onion
Add the ground beef to the skillet; cook, breaking apart with a spoon, until crumbly and browned, 2 to 4 minutes. Once done, transfer the beef to a bowl and leave the juices in the skillet.
1 ½ lb lean ground beef
While the beef cooks, peel and mince the garlic; transfer to a small bowl.
4 cloves garlic
Once the beef has been transferred, add the onion to the skillet; cook, stirring frequently, until softened, 3 to 5 minutes.
While the onion cooks, trim and discard the ends of the eggplants; medium dice the eggplants into ½-inch cubes and transfer to a large bowl.
Add olive oil to the skillet, followed by the garlic, eggplant, and diced tomatoes; season with cinnamon, salt, and pepper. Cook, stirring occasionally, until the eggplant is tender, 8 to 10 minutes.
1 tbsp extra virgin olive oil
2 (14.5 oz) cans diced tomatoes
2 tsp cinnamon
1 tsp salt
1 tsp black pepper
While the eggplant cooks, shave the parsley leaves off the stems; discard the stems and roughly chop the leaves.
Juice the lemon into a small bowl.
Add olive oil, Dijon, salt, and pepper to the lemon juice; whisk together.
2 tbsp extra virgin olive oil
½ tsp Dijon mustard
¼ tsp salt
¼ tsp black pepper
Return the ground beef to the skillet and stir in half of the parsley (save the rest for garnishing).
To serve, place the moussaka on a plate, sprinkle with the feta and remaining parsley, and season with additional salt and pepper to taste. Add the arugula on the side and drizzle with the dressing. Enjoy!