Thinly slice the red onion and place in a bowl. In a separate bowl, mix apple cider vinegar, sugar, and salt until dissolved. Pour over the onions, and let sit for at least 30 minutes.

Making Guacamole

Prepare Guacamole

In a bowl, mash ripe avocados. Add lime juice, salt, diced tomato, chopped cilantro, and minced garlic. Mix until combined and set aside.

Making Corn Salsa

Prepare Corn Salsa

In a bowl, combine cooked corn kernels, diced red bell pepper, chopped green onion, chopped cilantro, lime juice, and salt. Mix well and set aside.

Cooking Salmon

Cook the Salmon

Heat a non-stick skillet over medium-high heat. Season the salmon fillet with salt and sear for about 4-5 minutes on each side or until cooked through and flaky. Remove from heat.

Assembling the Tostadas

Assemble the Tostadas

Lightly toast the corn tortillas in the same skillet until crispy. Spread a layer of guacamole on each tortilla, top with corn salsa, place the cooked salmon on top, and finish with pickled red onions and a sprinkle of sesame seeds.