This is a true Cali-style burrito—with lots of chunky guacamole.
1. Stir together onion, vinegar, 1/3 cup lime juice, and salt in bowl. Cover, and chill 20 minutes, stirring occasionally.
2. Meanwhile, blend cilantro, garlic, and remaining 2 Tbs. lime juice in blender until garlic is minced. Season with salt and pepper, if desired. With blender running, slowly pour in oil until dressing is well blended.
3. Toss avocado chunks in separate bowl with 1 Tbs. dressing. Season with salt, if desired.
4. Toss baby greens, cabbage, radishes, tomato, and carrot in large bowl with remaining dressing.
5. Arrange greens mixture and pepitas (if using) in center of each tortilla, then spoon avocado chunks over top, mashing down lightly to keep from spilling out of burrito. Remove onions from marinade with fork, and divide sliced onions among tortillas. Roll up tortillas, leaving one end open.