Toss chicken tenders with the marinade ingredients in a bowl and cover with plastic wrap. Marinate for about 1 hour before cooking, or overnight in the refrigerator.
Add marinated chicken tenders to a pot over medium-high heat and cook for about 5 minutes. Flip and continue cooking for an additional 5-minutes. Remove chicken from the pot and cut into small pieces.
To the same pot, add diced onions and minced garlic. Stir together and scrape the bottom of the pot to get the brown bits off. Saute for about 5 minutes until soft.
Add cooked great northern beans to the pot and add the chicken broth and lemon juice. Bring to a boil, reduce heat and let the soup simmer for about 10 minutes.
Take half of the soup and blend by either using an emersion blender or a regular blender and transfer back to the pot.
Add the cut-up chicken and the kale to the pot. Stir to combine and let soup cook for about 5 additional minutes.
Taste and adjust seasoning by adding more red chili flakes for spice, salt, black pepper, or lemon juice. Serve Immediately.