Place the peaches in a shallow bowl and brush with the oil, coating them completely. Drizzle 1 tablespoon of the honey on the peaches, sprinkle with the salt, and pour over 1 tablespoon of the lemon juice. Gently move the peaches around to coat them.
Heat a grill pan over medium-high heat. Grill the peaches cut side down until the edges have begun to soften and brown, about 5 minutes. Gently turn the peaches and grill until fork-tender but still firm, about 5 minutes more (the ripeness and size of the peaches may alter the timing). Transfer the peaches to a platter, skin side down.
Make the drizzle: In a small saucepan bring the remaining honey and juice to a gentle simmer over low heat. Stir and simmer to combine, 1 minute more. Drizzle over the peaches, sprinkle with the pistachios if using and serve.