From Rebirth of the Night Wiki

Being able to cook is a vital part of Minecraft and is needed in order to get anywhere in Rebirth of the Night.

To start off, there is the basic furnace referred to in-game as the Rock Furnace. This furnace can easily be crafted as soon as you spawn in as it only requires eight rocks to be made.

Another Furnace that can be made fairly early on is the Blast Furnace. This furnace requires five iron ingots, one Rock Furnace, and three Smooth Coade Stone. What's good about this furnace is that it cooks at twice the speed of a normal furnace while still using the same amount of fuel.