Finely chop the onion and mince the garlic cloves, then finely chop the fresh parsley and set aside. Preheat your oven to 400°F and line two baking sheets with parchment paper. Having everything prepped and ready will make mixing the meatball mixture quick and efficient.

In a large bowl, combine the ground beef, chopped onion, minced garlic, eggs, parsley from Step 1, panko breadcrumbs, cumin, oregano, cinnamon, salt, pepper, and nutmeg. Mix gently with your hands until just combined—avoid overmixing, which can make the meatballs dense and tough. I find it helps to use a light touch and stop as soon as everything is evenly distributed. The mixture should feel moist but hold together when squeezed.

Using your hands or a small cookie scoop, form the mixture into 30 golf-ball sized meatballs (roughly 1.5 inches in diameter). Arrange them evenly on the prepared baking sheets, spacing them about an inch apart to allow for even browning. I like to slightly dampen my hands between rolls to prevent sticking.

Place both baking sheets in the preheated 400°F oven and bake for 20 minutes, until the meatballs are golden brown on the outside and cooked through (they should register 160°F on an instant-read thermometer). If needed, rotate the pans halfway through baking for even browning, though this isn't always necessary.

Transfer the warm meatballs to a serving platter and drizzle or dollop generously with the tzatziki sauce. Garnish with any remaining fresh parsley if desired for color and freshness.