If so, I bet you've spent some time in the Southwestern states, where this cactus apple (or tuna as they are called in South America) grows wild. The fruit of the prickly pear cactus is enjoyed throughout Mexico and South America. It's usually enjoyed fresh, but is also made into drinks and jellies. I found tuna fruit at my local Latin grocery. It must be peeled carefully to remove the spines, which are small and sharp, but the rewards are worth the effort. The spines had already been removed from the fruit that I bought.
The fruit tastes like blackberries and cantaloupe, and the texture is more like watermelon. It has many small seeds that you just crunch up and eat. If you have access to lots of cactus apples and are inspired to make homemade cactus apple jelly (when you are making jelly you strain out the seeds), here's an interesting food blog with a detailed recipe. Be sure and let us know how it tastes in the South American Food forums. I've never tried it but it sounds delicious, and it's such a beautiful color. A jar of homemade cactus apple jelly would make a great holiday food gift!