Place strawberries and sugar in a large skillet with the heat turned off. Stir well and allow to sit for at least 10 minutes.This will allow some of the liquid to release from the berries.
While the strawberries are macerating, dice the peppers finely. If you want less heat, scrape out the seeds before dicing. I left the seeds from both serrano peppers and found the heat level to be pleasant and not overly intense. Stir the peppers and seeds, if using, into the strawberries and sugar. Add the lemon juice.
Turn the heat to medium and allow the mixture to come to a simmer, stirring frequently. The skillet will slowly fill with more liquid as it releases from the strawberries. Continue stirring the jam as it simmers until most of the liquid has evaporated or thickened up. This may take anywhere from 15-30 minutes. Keep in mind that the jam will continue to thicken once it cools.
Once the jam is thick, remove it from the heat. Can, freeze or store in the refrigerator for up to one month.