Place sliced red onion into a small bowl. Add juice of one lemon and let sit.
Add chicken and salsa verde to Crockpot™ Express Oval Pressure Cooker. Cook on poultry setting and high pressure for 35 min.
To make an avocado crema, add avocado, juice of one lime and pinch of salt to the blender. Set aside.
Once chicken is ready, let it naturally release pressure so that the chicken stays juicy. Open lid and shred chicken apart with two forks.
Spread avocado crema onto tostadas.
Top with salsa verde chicken (replace chicken with pinto beans for plant-based option), shredded lettuce, lemon infused red onion, cilantro, jalapeño and carrots in escabeche.