It is die Scheibe, der Käse, die Portion and der Salat. Why do they have different indefinite articles?
closed as off-topic by Hubert Schölnast, Eller, Torsten Link, Jan, Björn Friedrich Aug 11 '17 at 9:20
This question appears to be off-topic. The users who voted to close gave this specific reason:
- "This site is about the usage and rules of the German language. It is not well-suited to replace dictionaries, grammar books or similar. If you have already consulted such general references and still have questions, please edit your question to explain what you found and why it did not help. See this post on Meta for more information." – Hubert Schölnast, Eller, Torsten Link, Jan, Björn Friedrich
Ein Portion Salat is simply incorrect; as you point out, Portion is feminine so the indefinite article must be eine.
The genus of the second noun — cheese and salad in your examples — is irrelevant, by the way. In this construction, the first noun carrying an article describes the quantity of the second noun; the latter never carries an article. Since the article belongs to the first noun, all three grammatical genders can follow without the article changing:
Ich nehme eine Scheibe Brot (neuter), eine Scheibe Käse (masculine) und eine Scheibe Wurst (feminine).