Preheat oven to 425℉. Place the prepared brussels sprouts on a baking sheet and pour on the olive oil, salt, and pepper. Mix with clean hands. Place the pear halves, cut sides-down, on the baking sheet, making sure there is enough oil to coat their cut surfaces.
Roast the brussels sprouts and pear for about 20 minutes. Then turn the brussels sprouts with a metal spatula so that both sides will get caramelized. Check the pear - it may not be caramelized at this point.
After another 10 minutes, turn the brussels sprouts again. Flip the pear. Reduce the oven heat to 375℉.
Add the pistachios - you just want to heat them up and toast them slightly.
After 5 minutes, remove the baking sheet from the oven. Squeeze lemon juice over all the ingredients. Use your spatula to chop up the pear halves. Toss everything thoroughly, check the seasoning, and serve on a platter or in a bowl.
