What are the similarities of the Spanish way of cooking and the Mexican way?

With the exception of using a lot of fresh ingredients there is not much similarity, including the ingredients.

The food is not hot.

The food is Mediterranean type concentrating on fish/seafood, poultry, meat, and fresh vegetables. The major spices used are salt, black pepper, garlic, onions, Spanish Paprika, and to a lesser extent saffron (because of cost). Olives and olive oil are very popular. Bread is baked, and purchased daily like the French and Italians do. Fresh local fruits are popular. Tropical fruits were not raised in Spain, it is not a tropical climate, so they are being introduced to the market as imports. Spanish Tortillas are like a 1/2" - 3/4' thick omelete and the Tortilla de Patata (Potato Tortilla) is world famous. They don't use flour or corn tortillas. Cured ham and many cured pork sausages are very popular.