Is heating up butter and putting it in popcorn a solution?

A solution is a homogeneous mixture of two or more substances. In the case of popcorn, the butter is not homogeneously mixed with the popcorn. The butter is a liquid and the popcorn is a solid, so the two substances are not in the same phase. Additionally, the butter is not evenly distributed throughout the popcorn, so the mixture is not homogeneous.

Therefore, heating up butter and putting it in popcorn is not a solution.