Is the word manteiga the same in Brazilian and European Portuguese?

Yes

The word "manteiga" is identical in meaning, spelling, and grammatical function in both Brazilian and Continental Portuguese. The only difference lies in pronunciation:

• The "t" sound: In most regions of Brazil, the "t" is affricated, sounding like the "ch" in "cheese" ([tʃ]). In Portugal, the "t" is a dental sound ([t]), where the tongue touches the back of the teeth.
• Vowel quality: Brazilian Portuguese tends to have more open and clearly articulated vowels. In Continental Portuguese, vowels are often more closed or reduced, making the word sound shorter and more "clipped."

Brazilian Portuguese Examples:

1. Eu gosto de passar manteiga no pão. (I like to spread butter on bread.)
2. Você comprou manteiga no mercado? (Did you buy butter at the market?)
3. A manteiga derreteu muito rápido. (The butter melted very quickly.)
4. Eu prefiro manteiga sem sal. (I prefer unsalted butter.)
5. Guarde a manteiga na geladeira. (Keep the butter in the fridge.)

Continental Portuguese Examples:

1. Gosto de barrar manteiga no pão. (I like to spread butter on bread.)
2. Tu compraste manteiga no supermercado? (Did you buy butter at the supermarket?)
3. A manteiga derreteu depressa. (The butter melted quickly.)
4. Prefiro manteiga sem sal. (I prefer unsalted butter.)
5. Põe a manteiga no frigorífico. (Put the butter in the fridge.)