Bring a large pot of salted water to a boil. Add the pasta and cook according to package instructions until al dente. Reserve about 1/2 cup of pasta water before draining.

While pasta is cooking, prepare the salad. In a small bowl, whisk together 1 tablespoon of olive oil or melted butter and the juice of half a lemon. Season with salt to taste.

Dice the cucumber and tear the lettuce into bite-sized pieces. Combine in a medium bowl. Just before serving, pour the lemon dressing over the salad and toss gently.

For the sauce, heat 1 tablespoon of oil or butter in a pan over medium heat. Add the drained tuna and break it up slightly with a spoon. Cook for 1-2 minutes.

Reduce heat to low. Stir in the sour cream or heavy cream and the grated cheese. Cook gently, stirring until the cheese is melted and the sauce is combined, about 2-3 minutes. Do not boil.

Add the drained pasta to the pan with the sauce. Add a splash of the reserved pasta water (about 1/4 cup) and toss everything together until the pasta is coated in the creamy sauce. Add more pasta water if needed for desired consistency.

If using optional eggs, you can quickly fry or poach them now.

Serve the creamy tuna pasta immediately, topped with fresh herbs if using. Serve the lemon cucumber salad on the side.