Synthesis of ethyl methyl ketone from 2-(4-hydroxyphenyl)ethyl methyl ketone
There are a number of ways to accomplish your goal, but they all involve several synthetic steps. As mentioned in the comments, it's always easier to buy a compound then run a reaction, but if you had a small amount of some exotic derivative, you could convert it to methyl ethyl ketone.

One possible route would be to convert the raspberry ketone to an ester using the Baeyer-Villager reaction.  In this reaction the secondary (ethyl) branch migrates in preference to the primary (methyl) side.  The resulting ester can then be converted to the desired ketone by any number of methods such as the Weinreb route.