Preheat your oven to 450ºF and line a half sheet pan with parchment paper.
Slice the sweet potatoes lengthwise before coating in 1 tablespoon of olive oil. Place the potatoes on the sheet pan cut side down and add a pinch of kosher salt over the tops.
Bake for 40-45 minutes until the potatoes are easily pierced with a fork and browned around the edges of the bottoms.
In the last 15 minutes of baking the potatoes, start on the beef.
To Make the Ground Beef and Spinach
Heat a large skillet over medium-high heat with 1 teaspoon of olive oil. Once hot, add the ground beef. Cook for 3-4 minutes to brown one side before adding the red onion.
Break the beef apart with a spatula and cook for another 3-4 minutes until the beef is fully cooked and the onion has softened.
Add the garlic, vinegar, honey, Worcestershire, broth or water, and black pepper to the pan. Cook for 1-2 minutes until the sauce thickens and evenly coats the beef and onion.
Turn off the heat and add the chopped spinach and 2 ounces of crumbled feta cheese to the pan. Stir everything together to wilt the spinach before serving. Salt to taste.
To Assemble
Flip the roasted sweet potatoes over on the sheet pan and press down in the center to create a well.
Spoon the ground beef and spinach mixture into the potatoes.
Sprinkle the remaining 2 ounces of feta over the top and finish with an optional pinch of chili flakes and honey drizzle.