Cheesy tomato and ricotta lasagne

CHEESY TOMATO AND RICOTTA LASAGNE 
Ready in: 45 minutes 
Prep: 15 minutes
Cook: 40 minutes
Serves: 4-5 people

Cheesy tomato and ricotta lasagne
1 brown onion, finely diced 
2 tablespoons lasagne herbs (see recipe below)
70g tomato paste 
½ teaspoon salt
½ cup red wine or vegetable stock
1 x 680ml jar tomato passata 
1 carrot, grated
3-4 x 100g sheets fresh lasagne pasta (or sheets about same size as your baking dish)
120g baby spinach leaves, roughly chopped 

from
http://www.stuff.co.nz/life-style/food-wine/recipes/97026292/Cheesy-tomato-and-ricotta-lasagne