In a large nonstick sauté pan over medium heat, toast the pine nuts, stirring occasionally to avoid charring, until golden and fragrant, about 5 minutes (but keep an eye on them). Transfer to a bowl.

In the same pan over medium-high heat, add ⅓ cup of water and the Brussels sprouts, cover tightly, and cook until just tender, about 8 to 10 minutes, depending on their size, stirring once to keep them from scorching on the bottom. Add the butter, cinnamon, sumac, salt, and pepper. Cook, uncovered, for 3 minutes, stirring often. If the water has evaporated before the sprouts are fork-tender, add another tablespoon or two.

Stir in the garlic and lemon zest and juice, and cook until the Brussels sprouts are fork-tender or are still firm but offer little resistance when pierced with a knife, about 30 seconds. Larger Brussels sprouts may take more time, of course, so you may want to add another teaspoon of butter and 1 to 2 tablespoons more water. Taste and adjust any seasonings. Finish with a drizzle of olive oil. Sprinkle the pine nuts on top and serve.