Make the panade
Adjust an oven rack to lower-middle position and preheat the oven to 400°F / 200°C. Combine the saltine crackers, eggs, buttermilk, garlic, parsley, cheeses, salt, and several grinds of pepper in a large bowl. Squeeze with your fingers until the paste resembles wet oatmeal.
Add the meat
Add ground beef and ground pork. Mix gently by hand until just uniform. Stop before it feels springy or sticky.
Check seasoning
Microwave or pan-fry a teaspoon of the mixture for 10–15 seconds until cooked through; taste and adjust salt and pepper levels in the raw mixture, repeating as needed.
Shape the loaf
Line a rimmed baking sheet with foil or parchment and lightly oil it. Shape the mixture into a large free-form loaf and insert a thermometer probe into the center (if using).
Bake
Transfer to the oven and bake until internal temperature reads 150°F / 66°C, about 45 minutes. (If using a leave-in thermometer, set target to 150°F and let carryover finish.)
Rest
Remove from oven and rest on a cutting board 10–15 minutes. The center will rise to about 160°F / 71°C.
Make the sauce
While resting, heat crushed tomatoes with olive oil, basil, and salt in a medium saucepan until simmering. Maintain a bare simmer until the meatloaf is rested and ready to serve. Discard basil and adjust seasoning with more salt as desired.
Serve
Transfer the meatloaf to a serving platter and spoon sauce all around it. Set the loaf in the center, slice thickly, and finish with Pecorino, parsley, and olive oil.