Preheat your oven to 375°F (190°C) and lightly oil a 9x9 baking dish.
Cook onion and garlic in a skillet with a little olive oil until they smell good.
Add the ground beef, brown it, and drain any extra grease.
Stir in the seasonings and salsa, let it simmer a few minutes until it thickens, then set it aside.
Slice the zucchinis thin (lengthwise) and pat them dry so the lasagna doesn’t get watery.
Start layering: meat on the bottom, then zucchini, then sour cream, then cheese — repeat until everything’s used, ending with cheese.
Cover with foil and bake for about 20 minutes.
Remove the foil and bake another 10 minutes until the cheese is bubbly and golden.
Let it rest for 10 minutes before slicing; add cilantro or avocado if you want.