Make marinated onions and salad dressing: Slice the onion into thin rings and place them in the bottom of a mason jar (or a container or bowl). Pour over the oil, lemon, garlic and spices. Give them a toss, cover and set aside until ready to assemble.
Toast Breadcrumbs: Heat a small skillet over medium heat and add panko. Toast for 2-3 minutes until golden brown, stirring often to avoid burning.
Add Spring mix blend to a large bowl or serving dish. Sprinkle with salt and pepper.
Arrange avocado and tomato on top of lettuce.
Add your marinated onions with a fork, leaving dressing remaining to dress the salad.
Top with freshly grated parmesan and toasted panko.
Dress the salad and serve immediately!