Black Bean Soup With Lime-Pickled Red Onions

Soup

• 3 Tbsp olive oil
• 2 cups chopped onion
• ³⁄₄ cup diced celery
• 2 ¹⁄₂ tsp finely chopped garlic
• 2 ¹⁄₂ tsp ground cumin
• 1 ¹⁄₄ tsp oregano
• ³⁄₈ tsp chipotle chili powder plus more for a spicier taste
• Kosher salt
• 4 (15 oz) cans black beans, rinsed well and drained
• 5 cups low-sodium chicken broth or stock (can use vegetable stock as well), plus more if needed
• 2 cinnamon sticks, broken in half

Garnish

• 1 large red onion
• ¹⁄₄ cup lime juice
• Kosher salt
• ¹⁄₂ tsp sugar
• 1 Tbsp chopped cilantro, plus 2 tsp more for garnish
• 2 ripe avocados, cut into ¹⁄₂ inch cubes