While the cod is curing, prepare the creamy green bean and pea salad by blanching the green beans and frozen peas. Wash and trim the green beans then cut into ½-inch (1 ¼ cm) pieces. Have a large bowl of ice water nearby. Bring a large saucepan of water to a boil and add 1 tablespoon salt. Add the green beans, and boil for 3 to 5 minutes or until tender and crisp. Using a slotted spoon, transfer the green beans to the ice water and let rest for about 1 minute. Transfer the green beans to a clean tea towel to dry. Repeat the blanching process with the peas. Using the same saucepan, cook the peas for 2 minutes. Transfer them to the ice water to cool for 1 minute. Drain the peas and place on a clean tea towel to dry.
In a large bowl, add the green beans, peas, sour cream, wholegrain mustard, and chopped parsley, and stir to combine. Set aside.
For the herb butter, in a small bowl, combine the butter, herbs, lemon zest and juice. Set aside.
Prepare the tomatoes by washing and drying them. Put 5 tomatoes onto each skewer, then brush the tomatoes with oil, and season with salt and pepper.
Preheat the grill to medium-high heat. To prevent the code from sticking to the grates, brush vegetable oil over the grates. Place the cod filets over indirect heat and cook for 3 to 5 minutes per side or until the flesh is opaque and flakes easily when pierced with a fork.
While the cod is cooking, add the tomato skewers to the grill and cook for 3 to 4 minutes, turning often, until somewhat charred with the skin bursting but still keeping its shape.
Melt the herb butter in a skillet over the grill.
To serve, divide the green bean and pea salad among 4 plates and place the grilled cod on top. Remove the tomatoes from the skewers and serve alongside the cod. Drizzle a good amount of the melted herb butter over the filets. Garnish with fresh herbs and serve immediately.