Cut the avocado in half lengthwise by sliding a knife into the avocado, until you reach the pit. For safety, place it on a cutting board. Rotate the avocado with one hand while keeping the knife steady with your other hand.

Rotate the avocado halves in your hands, twisting gently if necessary, and separate the two sections. Place the avocado half with the pit in a kitchen towel. Hold securely in your hand, and then carefully tap the back edge of a chef’s knife into the pit. Twist and then lift straight up to remove. Use a towel to remove the pit from the knife.

Scoop the avocado flesh out with a spoon and into a bowl. Use a fork to mash the avocado until it's mashed up to your desired texture.

Add the lime juice to the mashed avocado and stir.  This will slow down the oxidation process, which causes avocados, apples, bananas, etc. to turn brown after being cut.  If you are in a pinch and don't have lime juice, you can sub vinegar or lemon juice, it will just slightly alter the taste of the final product.  

Next, add in the pineapple tomato, onion, jalapenos, cilantro, and season with salt and pepper to taste.  You're done! Refrigerate and use within 24 hours.