Bring a large pot of lightly salted water to a boil. Add pasta and cook for 8 to 10 minutes or until al dente. When cooked, drain, then toss with olive oil and keep warm.
Meanwhile, melt 1 tablespoon butter in a frypan over medium-high heat. Sear the steaks on both sides until rosy-pink in the centre, 7 to 10 minutes depending on thickness. Remove steaks from pan and cut into bite-size pieces.
Melt the remaining 1 tablespoon of butter in the same frypan, and stir in the garlic and shallots. Cook 30 seconds until fragrant, then return the steak to the pan and cook for another 5 minutes or to desired doneness. Stir in the soy sauce, and cook a few seconds longer, allowing it to evaporate.
Remove the frypan from the heat and stir in the sun-dried tomato pesto, olives, spinach, basil, parsley, feta cheese and sunflower kernels. Toss with the pasta in a large bowl and serve.