Someone heated up a slice of frozen pizza on a meat oven tray. I noticed while the cheese on the pizza still hadn’t melted.
The only part of the pizza which actually touched the tray was the base.
Is the tray still kosher?
If the oven tray had not heated up at all yet, there is no concern. If it was already hot the pizza may have been absorbed into the grates, even through the base of the pizza.
Assuming no hot meat had been put directly on the tray in the last 24 hours, the tray can be kashered by heating the oven to the highest temperature for about 20 minutes.