It sounds like you are not intending to get the required license from the US Dept. Of Treasury prior to your trip and some how want to sidestep the issue by playing sleight of hand with your two passports. This will most likely end up very bad for you no matter how you do it.
From the US State Dept. page on Cuba
Tourist travel to Cuba remains prohibited. You must obtain a license
from the Department of Treasury or your travel must fall into one of
12 categories of authorized travel.
Travel to Cuba is regulated by the Office of Foreign Assets Control
(OFAC) of the U.S. Department of the Treasury. Anyone located in the
United States, regardless of citizenship and nationality, must comply
with these regulations. Individuals seeking to travel to Cuba are not
required to obtain licenses from OFAC if their travel is covered by a
general license. If travel is not covered by a general license, you
must seek OFAC authorization in the form of a specific license.
Travelers who fail to comply with regulations may face penalties and
And from §515.560 Travel-related transactions to, from, and within Cuba by persons subject to U.S. jurisdiction. you can see the twelve
words you can't say on TV categories approved for trips to Cuba, which are in summary
Official business of the U.S. government, foreign
governments, and certain intergovernmental organizations
Professional research and professional
- Public performances, clinics, workshops, athletic and other competitions, and exhibitions
- Support for the Cuban people
- Humanitarian projects
- Activities of private foundations or research or educational
- Exportation, importation, or transmission of information
or informational materials
- Certain export transactions that may be
considered for authorization under existing Department of Commerce
regulations and guidelines with respect to Cuba or engaged in by
U.S.-owned or -controlled foreign firms
While I love how they make the rules for the entire planet, you having a US passport makes it highly likely that they will come after you once they find out. And getting off a plane from Cuba and presenting your US passport will raise a huge flag to the authorities and you would end up answering a lot of embarrassing questions.
I would also not be surprised if the US authorities are in general watching flights to Cuba.