Bring a large pot of water to a boil. Cut zucchini into long thin strips with a spiralizer or vegetable peeler. Place in a colander set over a large bowl. Toss with 1/4 tsp. salt and let drain for 15 to 20 minutes. Meanwhile, pulse almonds in a food processor until coarsely chopped. Add tomatoes, 1 cup basil leaves, garlic, and crushed red pepper; pulse until coarsely chopped. Add 2 Tbsp. oil and 1/2 tsp. salt and pulse until combined; set aside. Cook spaghetti in the boiling water according to package directions. Drain and transfer to a large bowl. Gently squeeze the zucchini to remove excess water; add to the bowl with the spaghetti. Heat the remaining 1 Tbsp. oil in a large skillet over medium-high heat until shimmering. Season salmon with pepper and the remaining 1/4 tsp. salt. Add the salmon to the pan; cook until the underside is golden and crispy, about 4 minutes. Flip the salmon and cook until it flakes when nudged with a fork, 2 to 4 minutes more. Transfer to a plate and use a fork to gently flake it apart. Add the pesto to the spaghetti mixture; toss to coat. Gently stir in the salmon. Top with the remaining 1/4 cup chopped fresh basil. Garnish with Parmesan and additional pepper, if desired.