Lukewarm about food?

Is it natural to say :

Which is correct?

What foods are best eaten at a lukewarm temperature/are best eaten lukewarm?

Can you say “lukewarm”? Can you describe burger as freshly made”? Would you use “it” or “I”?

The burgers are always lukewarm so although they are freshly made, it feels/I feel like they’ve been sitting on the counter forever.

Thank you