If your child keeps asking for the same food meal after meal, the child is on a "food jag," especially common in the toddler years.
Although generally not harmful to kids, food jags can be frustrating to parents trying to promote a varied menu. It's OK to offer the same foods again and again, just include other foods alongside to encourage variety. Most "monotonous diners" soon tire of eating the same food so often.
If your child rejects whole categories of food for more than two weeks, talk to your child's doctor or a registered dietitian nutritionist.