DD1 went through this at 20 months - all she would eat was plain cooked pasta (no sauce!). I got around it by getting ravioli with vegies inside so she would eat something a bit more nutritious! She would however eat at childcare and other people's houses so it seems to be more of a control thing. I would do a tasting plate with bits of everything eg cheese, vegies, fruit, pasta etc and she would pick and choose what she wanted from the plate. She eats most things again now though so the phase did pass.