Preheat the oven to 425°F (220°C). Arrange a rack in the center. High, dry heat will encourage the sweet potato rounds to caramelize and develop golden edges rather than steam — that caramelization is where the flavor comes from.

Slice the sweet potato into 1/3–1/2-inch (8–12 mm) rounds. Try to keep them similar thickness so they cook evenly; thicker slices stay creamier, thinner will crisp more. If the rounds are different sizes, place larger ones toward the outside of the pan where heat is a bit stronger.

Toss the rounds in a bowl with 1 tablespoon olive oil, 1/4 teaspoon black pepper and 1/4 teaspoon of the 1/2 teaspoon salt (reserve the other 1/4 teaspoon). Coating them in oil does two things: it conducts heat to the surface so they brown, and it helps seasonings adhere.

Arrange the rounds in a single layer on a rimmed baking sheet lined with parchment or a lightly oiled sheet, leaving a little space between them so air can circulate. Crowding the pan traps steam and prevents crisp edges.

Roast for 12 minutes, flip each round, then roast another 10–13 minutes until edges are golden and centers are fork-tender. Flipping encourages even browning on both sides; total time depends on thickness and your oven. If you want extra char, finish with 1–2 minutes under the broiler, watching closely so they don’t burn.

While the potatoes roast, make the salsa: combine the diced tomato, finely diced red onion, chopped cilantro, 1 tablespoon lime juice and the remaining 1/4 teaspoon salt in a bowl. Stir and let rest for 5–10 minutes — the resting time lets the lime and salt draw juices from the tomato and marry the flavors.

Prepare the avocado: scoop the flesh of 1/2 avocado into a small bowl and mash gently with a fork until slightly chunky. Season with a pinch of salt, a squeeze of lime (if you like), and a tiny drizzle (1 teaspoon) of olive oil if you want silkier mouthfeel. Leaving it slightly chunky gives a contrast to the roasted potato textures.

Assemble: place warm sweet potato rounds on a serving plate, top each round with about 1/2–1 tablespoon mashed avocado, then spoon the fresh tomato salsa over the top. Finish with a small pinch of coarse sea salt or flaky salt and an extra grind of black pepper if desired. Serving while the rounds are still warm highlights the contrast between caramelized sweet potato and cool salsa/avocado.

Serve immediately as an appetizer, snack, or light main with lime wedges on the side. Leftovers: keep components separately (potatoes and salsa/avocado) in the fridge for up to 2 days; re-crisp potatoes in a hot oven for 6–8 minutes before serving and refresh avocado/salsa.