Reduce heat to medium and continue to cook onions, stirring frequently, until they turn golden brown and caramelized. Be patient - this may take up to 30 minutes.
Preparing greens:
Place a steamer basket inside a large pot with a tight-fitting lid and bring 3 inches of water to boil over high heat.
Add greens to the pot and steam until bright green and wilted, about 3-4 minutes, careful not to over-cook.If the greens turn brown that means they're overcooked.
Remove greens from pan and let cool in a large bowl.
In a small bowl, whisk together lemon juice, olive oil, garlic, salt and pepper; set aside.
Before adding the lemon vinaigrette to the greens, use a kitchen towel or paper towel to remove any excess liquid that may have formed.
Drizzle lemon vinaigrette over the greens and toss well to combine. Check for seasoning and adjust accordingly. Spread greens out in a thin layer on a large platter.
Top greens with caramelized onions and serve with pita bread warm, room temperature or chilled.