I have a very determined 2 y/o picky eater as well. I used to allow it to frustrate me to no end and i did exactly what the others are saying and that is give very small portion, lots of praise when she does eat but I dont reward her for eating other than giving praise.

some days she eats some day not. I also serve alot of leftovers as well as home made stuff. very rare that i used processed or boxed food. If she doesnt eat at lunch, i warm it for her snack. If she eats it then, she gets her snack as well.