Blend the tomatoes, onion, garlic & tomato sauce in a blender. Put aside.
Add the bay leaf & cloves to a big pot of water. Let it boil for about 15 minutes. Remove. Add spaghetti and cook according to instructions. Do not salt the water. Drain and set aside.
Melt the butter in a medium pan. Add blended tomato sauce & chicken bouillon.
Saute till it deepens in color ~5-7 minutes. Remove from heat.
Add the crema agria to tomato sauce. If you taste the sauce at this point it should be on the salty side. I also like to add a pinch of dried parsley at this point too.
Combine the spaghetti, ham and tomato sauce in a 9x12 casserole dish. Mix really well. Sprinkle the cheese over the whole casserole. Cover with foil and put in oven for 15 minutes or until heated through and cheese is melted.
*Crema agria can be found in the refrigerated mexican section but in a pinch sour cream can be used instead.