Squeeze lemon all over top of the crab patty, then place on bun (if using).
If your child is comfortable grasping and chewing larger food items, or if you want him/her to be more comfortable, this is an ideal vessel given its soft but sturdy package: cut into halves or quarters and allow your child to bite and consume at his/her own pace. Otherwise, press the sandwich down and cut into smaller bites or strips. You can use the sandwich to introduce creamy sauces/dressings, such as tartar ranch, and/or remoulade.
Pretty much any shellfish (shrimp, lobster) or whitefish could be substituted here; heck, chicken or turkey could work as well. You can take out the cauliflower altogether–though no one will ever know it’s there–or sub in spinach or another leafy green.
Most large chain grocery stores will carry chunk crab in 8oz containers. The recipe is designed for--and the example in the accompanying photo shows--claw meat; some grocery stores may carry packaged knuckle meat, which will be more expensive but has a richer mouthfeel.