Almond paste is somewhere in the middle between almond butter and marzipan. Almond butter is usually unsweetened and oily like peanut butter, and not as thick as almond paste. Marzipan is basically more finely-ground almond paste with more sugar (about twice as much) and sometimes egg whites. It is much drier than almond paste so that you can roll it out, which you definitely couldn’t with almond paste. Almond paste tastes more “almondy” than marzipan, simply because the ratio of almonds to sugar is higher in the paste.
Almond paste is sold premade at most stores, for use in decorating desserts and in making some baked goods. Some commercial almond paste also contains ground apricot kernels (heated first to make them safe.)
There are many recipes to make your own if you get stuck and can’t get to a store. Some call for egg whites, (which I’m a bit nervous about if I need to store the almond paste for any length of time, or use it on top of a baked good that will be unrefrigerated). The following procedure is a bit unorthodox in calling for the lemon juice, but is quite good (you want completely orthodox, make the schlep to the store). Whiz 1 cup of blanched almonds in a food processor or blender until very finely ground (or start with 1 1/8th cup of ground almonds). Then add 3 tablespoons of lemon juice and 1 cup of sugar, whiz till combined. Best made a day or two ahead of time; if desired you can enhance flavour with a bit of almond extract. If you need to double or triple the recipe, it may be best to make it in separate batches.
Another nut paste. Marzipan, surprisingly, is not a good substitute.
8 oz almond paste = 1 3/4 cups
After opening the tube or can of almond paste, store refrigerated in a sealed container for up to a year (some say two years.) If you have any cheesecloth to hand, a slightly-dampened piece of it on top the paste can help to keep it soft. If it does harden during storage, zap for 2 or 3 seconds in the microwave on high to soften.
In Sicily, it is called “pasta reale”, meaning “royal dough.”