Get a middle size bowl and set it aside

Take your onion and make middle dice cuts. then place it the bowl

Cut the mango in half, while removing the seed. make little squares cuts inside the fruit and take the knife and remove the skin. I would just look up a tutorial on YouTube about it. but when you're done place it in the bowl

with the plum tomatoes, quarter them and remove the seeds. middle dice as well and place it in the bowl

for the heat cut the jalapeno in half after you remove the stem. remove the seeds inside and fine dice the pepper.

Fine chopped cilantro or rough chop, its up to you. I like mine roughly chopped

juice the lemon over the ingredients in the bowl and stir. add salt for taste

enjoy :D