Thinly slice shallot by hand or on a mandolin. It's important to get thin slices. I usually set my mandolin to the thinnest setting.
Place the shallot slices in a strainer and sprinkle with the salt. Mix well. Set the strainer in a bowl or in the sink and leave the onions to drain for at least 15-20 minutes.
While the shallot is getting its salt soak on, place the frozen peas in a small bowl and cover with lukewarm water to thaw. You may have to change out the water once. It takes about 10 minutes for the peas to defrost.
While the peas and shallots are doing their thing, cut the cherry tomatoes into small slices. You can also quarter them, or if they are larger cherry tomatoes, you can cut them into eighths. Place in a medium mixing bowl.
Cut the avocado into cubes and place in the mixing bowl.
Drain the defrosted peas and add them to the mixing bowl with the cherry tomatoes and avocado.
By now the shallots should have softened up nicely. They should be very limp versions of their previously firm selves. Throughly rinse the salt off the shallots under cold water. Once rinsed, add to the mixing bowl.
Add the lime juice, sugar, and olive oil to the mixture.
Mix all the ingredient well. You shouldn't have to add any salt as the soaked onions will still have a little salt on them.
Serve chilled. Will store for a couple of days in the fridge.