Preheat the oven to 425 degrees.

On a parchment lined baking sheet, toss the fennel with 1 tablespoon olive oil and 1/4 teaspoon salt. Arrange in an even layer. Roast in the middle of the oven until golden brown and caramelized, about 40 minutes, flipping them halfway through. Set aside.

Meanwhile, combine the pepitas, garlic, arugula, lemon juice, 1/3 cup olive oil, and 1/4 teaspoon salt in a food processor or blender and puree until smooth. Add more oil as necessary. Taste for seasoning. Transfer to a large mixing bowl.

When ready to eat, bring a large pot of salted water to boil. Cook the spaghetti according to package directions. Drain and immediately add to the pesto. Toss until fully coated.

Cut ricotta into cubes or shavings using a vegetable peeler.

Divide the pasta among 2 bowls and top with the crispy fennel and shaved ricotta salata. Serve warm or at room temperature.