The prickly pear cactus fruit is also called cactus fig, Indian fig, or tuna in Spanish.
The prickly pears are edible fruit, but they have many small hard seeds inside. You can peel them and eat them raw, but many people use the juice to make jelly, juice, candy, or vinaigrettes.
You can find prickly pears in most Mexican markets, farmers markets, and sometimes in natural food supermarkets stores. They will already have the tiny thorns removed. You might find the fruit either green or red. If they're red, they've ripened on the cactus, but green ones will ripen sitting out on your counter. These will never turn red, but will get softer and become a lighter green.
If you pick your own fruit from the cactus, BE CAREFUL. The fruit has tiny thin prickles called glochids that are easy to overlook. If you get them in your skin, they're painful. Use leather gloves or tongs to pick the fruit and then use a hard bristled brush to scrape the glochids off before trying to peel them.
NOTE: If you harvest prickly pear fruit in the wild, leave enough for birds and other small animals to eat.
HOW TO CUT AND PEEL PRICKLY PEAR FRUIT
1 Slice both ends of the fruit off and throw them away.
2 Cut a thin vertical slice down the length of the fruit.
3 Slip your finger underneath the slice and hold onto the skin.
4 The skin will easily peel off as you pull on it. You won't eat the skin so throw it away, too. The flesh will be full of little hard seeds, which are edible if you care to eat them. You may prefer to extract the juice.
If your fruit are large, you can probably get a cup of juice from 6 prickly pears. To make juice, place the peeled fruit into a blender or food processor and pulse until liquefied. Pour the pulp into a fine mesh sieve and push it around until the juice falls into out into your pitcher.
You can add juice to lemonade, cocktails, tea, carbonated water, and soda. You can also pour fruit into a fruit salad, over ice cream, into yogurt, etc.
You might experiment and use the pulp in desserts, yogurt, or other dishes.