Preheat the oven to 350 degrees F and line a baking sheet with foil or parchment paper.
Heat oil in small skillet over medium-high heat. Add onion and cook until softened (for more flavor, cook until golden brown). Add brown sugar, garlic, Italian seasoning and chili powder and cook for 1-2 minutes until fragrant. Set aside to cool slightly.
In a large bowl, combine ground turkey, bread crumbs, eggs, milk, Worcestershire sauce, ketchup, salt and pepper. Add the slightly cooled onions and mix to combine (don't overmix).
Shape into two equal loaves (you can do one but you'll need to add 15-20 minutes to the cook time), roughly 6" by 4".
Stir together the glaze (ketchup, brown sugar, cider vinegar) and brush on top of the meatloaf.
Bake for 40-50 minutes, until a meat thermometer reads a minimum of 165 degrees F.
Let rest for 5-10 minutes before slicing.
Don't over-mix. Mix the meat mixture only until just combined. If you over-mix the meat can become dry and tough.
Make equal sized loaves. Be sure that you divide the meat mixture up into two even amounts so they cook at the same rate.
Check the temp. To verify that the meatloaf is done, use a meat thermometer. It should be 165ºF.
Let it rest. Let the meatloaf rest for 5-10 minutes before you slice into it so the moisture can redistribute. If you slice into it too soon, that moisture will run out and the loaf will be dry.
Storage:Leftover baked turkey meatloaf will last in an airtight container in the fridge for 3-4 days or in the freezer for 3-4 months. To reheat, thaw in the fridge if frozen then microwave until heated through.