Spicy chicken pasta

I just saw this recipe in Everyday Food (magazine). The recipe was published as 1 serving, but I modified the quantities and will post the amounts I used. I had enough for 2 servings + seconds for John + a small amount for me to have as left overs.

coarse salt
1 1/2 c. penne pasta (I used whole wheat)
~3/4 lb. chicken breast tender strips (not the cooked kind) cut in ~1" cubes
2 plum tomatoes seeded and diced
~5 T. tomato paste
3 cloves garlic - minced
~ 1 T. olive oil
1/2 t. red pepper flakes (plus more for sprinkling on top if you like the heat)
4 c. loose packed baby spinach
lemon juice (squeezed 1/2 a lemon)

bring salted water to a boil

cook pasta, adding chicken to the boiling water for the last 2-3 minutes. Make sure chicken gets cooked through during the boil. Reserve 1/2 c. pasta water.

Drain pasta and chicken.

In a large sauce pan (I used the wok) cook the garlic with the olive oil for 1-2 mins. Add the tomato paste, red pepper flakes and diced tomatoes.

Add pasta and chicken. Add lemon juice and enough water to form a thin sauce that coats pasta.
Add spinach, toss until spinach is barely wilted.

Serve immediately.