Step 1

Preheat oven to 375 degrees F. Coat a large rimmed baking sheet with cooking spray (or see Loaf Pan Variation).

Step 2

Pulse onion, bell pepper and celery in a food processor until finely chopped. (Or finely chop them with a knife.)

Step 3

Heat oil in a large nonstick skillet over medium-high heat. Add the vegetables and cook, stirring occasionally, until tender and most of the liquid has evaporated, 5 to 10 minutes. Transfer to a large bowl and let cool for 10 minutes.

Step 4

Add 2 tablespoons ketchup, Worcestershire, mustard, paprika, garlic powder, salt and pepper to the vegetables; stir to combine. Stir in egg and breadcrumbs. Add ground beef and with clean hands gently knead the vegetable mixture into the meat; do not overmix. Pat the meat mixture into a loaf shape (about 12 by 5 inches) on the prepared baking sheet. Spread the remaining 3 tablespoons ketchup on top.

Step 5

Bake the meatloaf until an instant-read thermometer inserted in the center registers 165 degrees F, about 45 minutes. Let rest for 10 minutes before slicing.