In skillet, heat 2 tablespoons of the oil; sauté almonds until golden brown. Remove from pan.
In same pan, heat remaining oil; sauté onion and garlic for 3 minutes. Stir in tomatoes, tomato paste, parsley, basil, salt, and red pepper flakes. Cook 2 minutes more. Stir in almonds; cook 2 minutes; remove from heat.
For each crostini, spread 1 scant tablespoon tomato mixture on each toast slice; sprinkle with grated Parmesan cheese. Allow 3 to 4 crostini per serving.