Peel the sweet potatoes and thinly slice them. I used a knife, but for better results, I recommend using a mandoline.
In a mixing bowl, sprinkle chilli powder and salt for seasoning. Mix well. Drizzle with oil, and mix well using your hands. The sweet potato slices should get a coat of the seasoning and oil on both sides.
Lightly oil a baking tray, place a parchment paper, and place the sweet potato slices.
Preheat the oven to 150 degrees Celcius (300 degrees F).
Bake for a total of 15-20 minutes. After the first 10 minutes, take the tray out, turn them over, and bake for another 10 minutes.
ATTENTION: You wouldn’t the entire 10 minutes after you turn them over. Keep a close eye, and take them out once they start turning brown (Usually around 5 minutes). This is why we want to slices to be even so that they get baked uniformly.
In a mixing bowl, add the deseeded, finely chopped, watermelon slices, chopped cilantro (coriander leaves), green chilli (deseeded and sliced), finely chopped onion, brown sugar, and lime juice.
Drizzle some vinegar, add a pinch of salt, and mix well.