Cut it in half, take out the pulp, put the halves skin side up in a pan. Fill 1/4 with water and bake until soft in a 350 or so oven.
when it's done and cooled a bit, scoop out the flesh and puree with a hand blender or food processor. Then, put in a sieve lined with cheese cloth or a tea towel and drain as much water as possible. after you can freeze it if you want to.
Easy, easy!