"There is a lot of tomato in the pasta."
Translation:Pastassa on paljon tomaattia.
Well, no. A minor thing is that you have an extra "a" in the end of tomaattia. But the main point is the word order(*). The theme, the topic, preferably comes first in a sentence. Later comes the rheme, what you say about the theme. Because of the influence of the Indo-European languages the verbs nowadays comes between those parts. Here the theme is the pasta, the rheme is a lot of tomato and you put the copula, the verb "to be", between those parts.
That theme–rheme order applies to all sentences and especially to existential clauses (something is somewhere) like this one. English with its "there is/are" constructions uses a different word order.
*: Having said that you could put the parts in other orders, incl. the one you suggested, but in those cases the order would be emphasising something and the English sentence would therefore be something else.