I've seen this somewhere, but cannot remember where and its very very easy.
All you need: frozen puff pastry (thawed out), salmon, pesto (homemade or store bought), tomato, salt/pepper.
Once you thaw out the puff pastry, place on foil on a baking sheet. On a separate piece of foil, place the salmon on it and season with salt and pepper. Bake at 400 degrees for 15 minutes. The puff pastry might cook quicker than the salmon so watch it!
Meanwhile, make the homemade pesto (an easy trick - Knorr has a pesto mix that you can make and its pretty good.) If going the store bought route, skip this step. Slice tomatoes. Once the puff pastry is ready. Take it out and drizzle some pesto sauce over it. Top with tomatoes.
Top that with the salmon. Drizzle a little more pesto on top. Done and done.