Purple Sweet Potatoes with Maple Tahini

2.5 lb. purple sweet potatoes, scrubbed and cut into 1/4 inch wedges

4 TBS. vegetable oil, divided

Kosher salt to taste

1/2 cup tahini

2 TBS. white wine vinegar

1 TBS. maple syrup

2 tsp. lemon zest

1 TBS. lemon juice

3 TBS. pine nuts

1/4 cup chopped dill

Place racks in upper and lower thirds of oven and set a rimmed baking sheet on each; preheat oven to 375°. Toss sweet potatoes in a large bowl with 2 Tbsp. oil; season with kosher salt and pepper. Carefully spread out half of sweet potatoes in a single layer on each baking sheet. Roast, turning halfway through, until golden brown, 30–35 minutes. Meanwhile, whisk tahini, vinegar, maple syrup, lemon zest, lemon juice, remaining 2 Tbsp. oil, and 2 Tbsp. water in a small bowl; season maple tahini with kosher salt and pepper. Toast pine nuts in a dry medium skillet over medium-high heat, tossing often, until golden brown, about 2 minutes. Transfer to a small bowl and let cool. Spoon some maple tahini into shallow bowls or onto plates and arrange potatoes on top. Scatter dill and pine nuts over and sprinkle with sea salt.