• Gather all ingredients for the meatloaf.

For Oven Method:

• Start by preheating your oven to 350°F. In a small skillet, melt the butter over medium heat. Add the onion and sauté until it becomes soft and lightly golden, about 4-5 minutes. Stir in the minced garlic and continue cooking for one more minute before letting the mixture cool slightly.
• In a large bowl, combine the diced bread with milk and stir well. Then add the ground beef, pepper jack cheese, chopped cilantro, minced chipotle peppers, chili powder, cumin, salt, pepper, beaten egg, and the cooled onion mixture. Mix all the ingredients together gently until just combined.
• Use nonstick spray to lightly coat a meatloaf pan, then transfer the meat mixture into the pan, shaping it evenly.
• In a separate small bowl, combine the ketchup, adobo sauce, and brown sugar. Spread half of this mixture over the top of the meatloaf. Bake it in the oven for 60 to 90 minutes, or until the internal temperature reaches 150-155°F. Allow it to rest for about 10 minutes prior to slicing, using the remaining sauce for drizzling or dipping as desired.

For Slow Cooker Method:

• To use a slow cooker, follow the first two steps as described for the oven method. Line a 4-quart or larger slow cooker with aluminum foil or parchment paper, creating holes to allow the grease to drain. Shape the meat mixture into a loaf and place it on the prepared foil.
• Top the meatloaf with half of the sauce you prepared earlier, then cover and cook on low for 4 to 5 hours, or until it reaches 150-155°F. After that, carefully lift it out, allowing the grease to drain off. If desired, broil it for a few minutes to caramelize the sauce for a sticky finish. Let it rest for 10 minutes before serving.