Pro tip: microwaves used in ovens have a wavelength of roughly 12 cm. This means that every 12 cm in the microwave oven there is a "node", a spot where there is no heating happening. This is why most microwave ovens have a turn table so your food moves around in that field of waves so it somewhat gets heated equally. The problem with turntables however is that what is at the center will remain at the same spot. This is why the center of the food remains cold. It sat in our near a node.

So the solution to alleviate the cold spot problem is to put your plate as far off center on the turntable as possible while allowing it to still spin and then shift it of to the opposite side of the turntable halfway through.