Heat the oven to 375°F. Lightly grease a small baking dish or line a rimmed baking sheet with parchment paper.
Heat the olive oil in a skillet over medium heat. Add the chopped broccoli and onion, then cook for 3 to 4 minutes, stirring occasionally, until the broccoli is just tender. Add the garlic and cook for 30 seconds. Set the mixture aside to cool slightly.
In a large bowl, combine the ground turkey, almond flour, egg, Dijon mustard, salt, and black pepper. Add the cooled broccoli mixture and shredded cheddar. Mix gently until evenly combined, taking care not to pack the mixture too firmly.
Shape the mixture into a loaf in the prepared dish or on the baking sheet. Bake until the center reaches 165°F, about 45 to 55 minutes.
Let the meatloaf rest for 10 minutes before slicing so it can firm up and hold together.